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Process technology of high-speed implant-apertured index-guide lateral-current-injection top dielectric-mirror quantum-well 850-nm vertical cavity surface-emitting lasers (VCSELs) has been developed. Oxygen and helium implantation for aperture definition and extrinsic capacitance reduction, dielectric mirror formation, p- and n-ohmic contact formation, VCSEL resistance, and thermal analysis were investigated. Employing this technology, GaAs/AlGaAs-based 850-nm VCSELs with small signal modulation bandwidths up to 11.5 Gb/s and an eye diagram generated at 12 Gb/s by a pseudorandom bit sequence of 2/sup 31/-1 were achieved. The bit-error rates were below 10/sup -13/. The threshold current is as low as 0.8 mA for 7-/spl mu/m-diameter current apertures and typical slope efficiencies of 0.45-0.5 mA/mW were obtained.

Results are presented on a lateral current injection vertical cavity surface emitting laser (VCSEL) structure, the implant apertured, index guided VCSEL (I 2 -VCSEL). This approach was previously used for 980 nm emission and has now been adapted for 850 nm emission. The threshold current is as low as 0.8 mA for 7 μm diameter current apertures. Typical slope efficiencies of 0.45–0.5 mA/mW are obtained for output mirror reflectivity of 99.5%. Small-signal measurements of the modulation response indicate instrument-limited bandwidths in excess of 11 GHz. Large-signal measurements demonstrate 10 Gb/s operation with bit-error rates below 10 −13 . In addition, high repetition rate pulses were generated by gain switching both single and multimode VCSELs. These Gaussian pulses had time bandwidth products below 2.5, pulse widths as low as 29.6 ps and timing jitter as low as 5.5 ps.

A self-aligned fabrication process for small emitter contact area (2×4 μm2) GaN/AlGaN heterojunction bipolar transistor is described. The process features dielectric-spacer sidewalls, low damage dry etching, and selected-area regrowth of GaAs(C) on the base contact. The junction current–voltage (I–V) characteristics were evaluated at various stages of the process sequence and provided an excellent diagnostic for monitoring the effect of plasma processes such as chemical vapor deposition or etching. A comparison is given with large emitter-area (1.96×103 μm2) devices fabricated on the same material. The small-area devices are attractive for microwave power switching applications provided a high-yield process can be developed.

The development of a self-aligned fabrication process for small emitter contact area ( 2×4 μ m2) GaN/AlGaN heterojunction bipolar transistors and GaN bipolar junction transistors is described. The process features dielectric-spacer sidewalls, low damage dry etching and selected-area regrowth of p-GaAs(C) on the base contact or n-GaN/AlGaN on the emitter contact. Series resistance effects are still found to influence the device performance.

Low resistance ohmic contacts are difficult to form on p-type GaN and AlGaN due to the relatively high ionization energy of Mg in GaN and AlGaN. A carbon-doped GaAs grown on p-GaN prior to ohmic metallization has been shown to improve contact resistance to p-GaN. npn AlGaN/GaN heterojunction bipolar transistors and GaN bipolar junction transistors have been demonstrated by employing a regrowth C-doped GaAs to the p-GaN base regions. GaN/AlGaN epilayers were grown with a molecular beam epitaxy system and C-doped GaAs (1020 cm−3) was regrown on the devices (∼500 A) by metal organic chemical vapor deposition using SiO2 as mask. Very high current densities were achieved for common base operation in both device types and devices were operable at 250°C.

High-density plasma etching of GaAs, GaSb, and AlGaAs was performed inICl/Ar and IBr/Ar chemistries using an Inductively Coupled Plasma (ICP)source. GaSb and AlGaAs showed maxima in their etch rates for both plamachemistries as a function of interhalogen percentage, while GaAs showedincreased etch rates with plasma composition in both chemistries. Etchrates of all materials increased substantially with increasing rf chuckpower, but rapidly decreased with chamber pressure. Selectivities >10 forGaAs and GaSb over AlGaAs were obtained in both chemistries. The etchedsurfaces of GaAs showed smooth morphology, which were somewhat better withICl/Ar than with IBr/Ar discharge. Auger Electron Spectroscopy analysisrevealed equirate of removal of group III and V components or thecorresponding etch products, maintaining the stoichiometry of the etchedsurface.

A parametric study of Inductively Coupled Plasma etching of InP, InSb, InGaP and InGaAs has been carried out in IC1/Ar and IBr/Ar chemistries. Etch rates in excess of 3.1 prrdmin for InP, 3.6 prnh-nin for InSb, 2.3 pm/min for InGaP and 2.2 ~rrdmin for InGaAs were obtained in IBr/Ar plasmas. The ICP etching of In-based materials showed a general tendency: the etch rates increased substantially with increasing the ICP source power and rf chuck power in both chemistries, while they decreased with increasing chamber pressure. The IBr/Ar chemistry typically showed higher etch rates than IC1/Ar, but the etched surface mophologies were fairly poor for both chemistries.

Heavily carbon-doped (p≥10 10 cm −3 ) GaAs layers were grown on p-GaN in attempt to reduce the p-ohmic contact resistance. While the specific contact resistances on the p-GaN and p-GaAs were typical of the current state-of-the-art (∼10 −3 and 10 −5 Ω cm 3 , respectively), the high valence band offset at the GaAs/GaN interface produced a barrier to hole transport. The specific contact resistance for the GaAs(C)/GaN(Mg) structure was better than that of GaN alone, but was still in the 10 −3 Ω cm 2 range, even after alloying of the metal at 800°C. Other approaches to lowering contact resistance on p-GaN are discussed.

Selective etching of GaAs over AlGaAs and InGaP was examined in different plasma chemistries (BCl3/SF6, BCl3/NF3, IBr, ICl, BI3, and BBr3) in a high density plasma reactor. The normal etch stop reactions involving formation of involatile AlF3, InF3, or InCl3 are found to be less effective under high density conditions because of the higher ion-assisted etch product desorption efficiency. Addition of SF6 to BCl3 produces higher selectivities than NF3 as an additive, while IBr, ICl and BBr3 are essentially non-selective for both heterostructure systems. Selective etching of InGaP over GaAs is achieved using the BI3 chemistry.

A parametric study of etch rates and surface morphologies of In-containing compound semiconductors (InP, InGaAs, InGaAsP, InAs and AlInAs) obtained by BClj-based Inductively Coupled Plasmas is reported. Etch rates in the range 1,500-3,000 &min. are obtained for all the materials at moderate source powers (500 W), with the rates being a strong function of discharge composition, rf chuck power and pressure. Typical root-mean-square surface roughness of-5 nm were obtained for InP, which is worse than the values obtained for Ga-based materials under the same conditions (-1 run). The near surface of etched samples is typically slightly deficient in the group V element, but the depth of this deficiency is small (a few tens of angstroms).

Two plasma chemistries, i.e., CH4/H2/Ar and Cl2/Ar, were compared for the etching of InGaP, AlInP, and AlGaP under inductively coupled plasma (ICP) conditions. While the etching with CH4/H2/Ar discharges appears to be ion driven, Cl2/Ar discharges showed an additional strong chemical enhancement. The highest etch rate (∼1 μm/min) for InGaP was achieved at high ICP source power (⩾750 W) with the Cl2/Ar chemistry. Cl2/Ar discharges provided very smooth surfaces in all three materials with root-mean-square roughness measured by atomic force microscopy around 2 nm. This result may be due to the efficient ion-assisted product desorption in this chemistry. The etched near-surface region of InGaP (∼100 A) with Cl2/Ar maintained almost the same stoichiometry as that of the unetched control. By contrast, the CH4/H2/Ar plasma chemistry produced somewhat rougher surfaces and depletion of phosphorous (P) from the surface of InGaP.

Inductively coupled plasma (ICP) etching of all of the main III–V compound semiconductors is reported as a function of source and chuck power, pressure and gas additive (Ar, N2, H2) in Cl2 plasmas. Etch rates between 2000 and 5000 A min−1 were obtained for all materials at moderate source power (750 W) and low d.c. self-bias (≤ −150 V). Surface morphologies were smooth over a broad range of conditions for Ga-based materials, while for In-based semiconductors there was a much narrower window of appropriate ion-to-neutral ratios to obtain smooth etched surfaces on In-based semiconductors.

Dry etching of InGaP, AlInP, and AlGaP in inductively coupled plasmas (ICP) is reported as a function of plasma chemistry (BCl3 or Cl2, with additives of Ar, N2, or H2), source power, radio frequency chuck power, and pressure. Smooth anisotropic pattern transfer at peak etch rates of 1000–2000A·min−1 is obtained at low DC self-biases (−100V dc) and pressures (2 mTorr). The etch mechanism is characterized by a trade-off between supplying sufficient active chloride species to the surface to produce a strong chemical enhancement of the etch rate, and the efficient removal of the chlorinated etch products before a thick selvedge layer is formed. Cl2 produces smooth surfaces over a wider range of conditions than does BCl3.

We report results of a study on the inductively coupled plasma (ICP) etching of GaAs, AlGaAs, GaSb, and GaP in pure Ar, and plasma chemistries. Etch rates of the semiconductors initially increase with ICP source power, reaching maxima around 1500 - with - 700 W ICP power, and then decrease with further increase of ICP power because of the decrease in cathode dc self-bias. Etch rates increase at fixed ICP power with rf chuck power in the range of 100 W to 450 W, while they showed little dependence on the chamber pressure (2 mTorr - 20 mTorr) in discharges. We found that the dc self-bias on the rf chuck decreased exponentially as ICP power increased, while it increased with rf chuck power and pressure in these plasma chemistries. A simple calculation of ion flux and etch yield based on dc self-bias of the plasmas on the sample chuck was used to measure typical values of etch yield. In both ICP and discharges these were close to the pure Ar sputter yield.

ICl/Ar and IBr/Ar plasmas were found to be promising candidates for room temperature dry etching processing of the III-V semiconductors GaAs, AlGaAs, GaSb, InP, InGaAs, and InSb. Results showed fast etch rates (0.7 µm/min in ICl/Ar and −0.3 µm/min in IBr/Ar), and at high microwave power, 1000 W, good surface morphology (typical root mean square roughness ∼2 nm), while retaining the near-surface stoichiometry, especially in IBr/Ar plasmas. There was little change of surface smoothness over a wide range of plasma compositions for Gacontaining materials in both ICl/Ar and IBr/Ar plasmas, (e.g. GaAs), while there was a window region with about 25–50% of IBr in IBr/Ar plasmas to maintain good morphology of In-containing semiconductors like InP. Selectivities of 4–10 over mask materials such as SiO2, SiNx, and W were typical in ICl/Ar plasmas.

BCl3/Ar and BCl3/N2 plasma chemistries were compared for patterning of InP, InAs, InSb, InGaAs, InGaAsP, and AlInAs. Under electron cyclotron resonance conditions etch rates in excess of 1 µm/min can be achieved at room temperature with low additional rf chuck power (150 W). The etch rates are similar for both chemistries, with smoother surface morphologies for BCl3/Ar. However, the surfaces are still approximately an order of magnitude rougher (as quantified by atomic force microscopy) than those obtained under the same conditions with Cl2/Ar. InP surfaces etched at high BCl3-to-Ar ratios have measurable concentrations of boron-and chlorine-containing residues.

BCl3/Ar discharges provide rapid, smooth pattern transfer in GaAs, AlGaAs, GaP, and GaSb over a wide range of plasma conditions. At high BCl3-to-Ar ratio there is significant surface roughening on GaSb, which is correlated with the presence of B- and Cl-containing residues detected by Auger electron spectroscopy. BCl3/N2 discharges provide similar etch rates to BCl3/Ar, but when used with photoresist masks lead to rough morphologies on the semiconductor materials due to enhanced dissociation and redeposition of the resist. Etch rates with electron cyclotron resonance discharges are up to two orders of magnitude higher than for rf-only conditions.

IBr/Ar plasmas were found to be promising candidates for room temperature dry etch processing of the III-V semiconductors GaAs, AlGaAs, GaSb, InP, InGaAs, and InSb. Results showed fast etch rates (∼3,000A/min) at high microwave power (1000W) and good surface morphology (typical root mean square roughness ∼2 nm), while retaining the near-surface stoichiometry. There was little variation of surface smoothness over a wide range of plasma compositions for Gacontaining materials. By contrast, there was a plasma composition window of about 25–50% of IBr in IBr/Ar plasmas for maintaining good morphology of Incontaining semiconductors like InP. Etch rates of the semiconductors generally increased with microwave power (400-1000 W) and rf power (50-250 W), whereas there was little dependence of the rates on the increasing percentage of IBr in the IBr/Ar plasma composition above 30% IBr for In-based, and 50% IBr for Ga-based materials. Those results show the etch rates over 30% of IBr in IBr/ Ar are desorption-limited. Photoresist masks do not hold up well to the IBr under ECR conditions, resulting in poor profile control, whereas SiNx offers much better etch resistance.

The effects of ion-induced damage in n- and p-type GaAs and p-type InP exposed to inductively coupled plasma (ICP) Ar discharges were measured by diode ideality factor and barrier height measurements. At fixed RF chuck powers, the electrical characteristics of the diodes generally improve with increasing ICP source power because the incident ion energy is decreased. In the particular case of p-GaAs, the higher ion flux at high-ICP source power leads to a degradation in barrier height. Exposure time and ion energy have a stronger influence than ion flux in all three materials. The results are compared to those obtained with electron cyclotron resonance Ar plasmas and show the same basic trends. The clear result is that at moderate ICP source powers, the suppression of self-induced dc bias on the powered electrode leads to a lower amount of ion damage to the semiconductors than for conventional reactive ion etch discharges.

High ion density plasma conditions are found to create severe reductions in carrier density and reduction in photoluminescence intensity in doped AlGaAs and InGaP during exposure to Electron Cyclotron Resonance SF6 discharges. These are typical of processes where SiNx or SiO2 are removed from an underlying semiconductor layer, and suggest that conventional reactive ion etching, or alternatively low power or high pressure ECR conditions are necessary to avoid ion-induced damage.

The etch rates of InGaP, AlInP and AlGaP are more than an order of magnitude larger in microwave-enhanced BCl3/Ar discharges relative to conventional reactive ion etch (RIE) conditions. This is due to the increased atomic radical and ion densities. While RIE discharges produce rough, non-stoichiometric surfaces of InGaP and AlInP due to the formation of an InCl3 selvedge layer, the surfaces of samples etched under ECR conditions are generally smooth and stoichiometric. This difference is found to be due to the efficient ion-assisted desorption of InCl3 under high ion density conditions. The advantage of this process is that simple BCl3-based plasma chemistries can be employed for all III–V semiconductors, whereas previously CH4/H2 was used for In-containing materials and chlorine chemistries for Ga-containing materials. The etch rate of AlGaP is substantially slower than the other two materials, which can be explained on the basis of the bonding differences.

ICl and IBr provide rapid etching of the ternary alloys InGaP, AlInP,and AlGaP under electron cyclotron resonance conditions. The rates are almost independent of microwave power in the range 400 to 1000 % with typical values of ∼1.5 μm/min with ICl/Ar and ∼0.4 μm/min with IBr/Ar. At low microwave powers (≤750 W), the etched surface morphologies are quite smooth and there is little degradation of photoresist masks. High Al content Al x Ga 1-x P (x ≥ 0.7) alloys appear to be good candidates as etchstop layers in InGaAlP device structures when using these plasma chemistries.

Cl{sub 2}-based plasmas for etching GaAs, AlGaAs, and GaP have been examined as a function of gas additive (Ar, N{sub 2}, or H{sub 2}), radio frequency (RF) and microwave power, plasma composition, mask material, and process pressure. In a load-locked reactor, smooth etched surface morphologies were obtained over basically all conditions investigated, with typical root-mean-square roughness of {le}1.5 nm measured by atomic force microscopy. The etch rates for all three materials increase with RF power (ion energy), microwave power (ion current), Cl{sub 2} percentage, and pressure, with controlled rates of {approximately}0.4 {micro}m/min at a condition of 2Cl{sub 2}/13Ar, 850 W microwave power, 1.5 mTorr, and 100 to 150 W of RF power. Operating under electron cyclotron resonance conditions where the ion density is {ge}5 {times} 10{sup 11} cm{sup {minus}3} (measured by microwave reflection interferometry) produces rapid degradation of photoresist, and more robust mask materials such as SiN{sub x}, SiO{sub 2}, or W are necessary.

High microwave power (1,000 W) electron cyclotron resonance CH{sub 4}/H{sub 2}/Ar discharges produce etch rates for In{sub 0.5}Ga{sub 0.5}P, Al{sub 0.5}In{sub 0.5}P{sub 0.5}, and Al{sub 0.5}Ga{sub 0.5}P of {approximately} 2,000 {angstrom}/min at moderate RF power levels (150 W) and low pressure (1.5 mTorr). This is approximately a factor of five faster than for conventional reactive ion etching conditions where much higher ion energies are necessary. The etched surfaces are smooth over a wide range of CH{sub 4}-to-H{sub 2} ratios and microwave powers. AlInP is more resistant to preferential loss of P from the near-surface during etching than is InGaP. While the etching is ion-driven, pure Ar discharges produce rough surfaces and the CH{sub 4}/H{sub 2} is necessary in the achievement of acceptable morphologies. The InGaAlP/GaAs heterostructure is being increasingly utilized in diode lasers, light emitting diodes, field-effect transistors, and heterojunction bipolar transistors.

Dry etching of III-V semiconductors under reactive ion etching, magnetron, or electron cyclotron resonance (ECR) conditions has been performed in the same reactor using the CH{sub 4}/H{sub 2}/Ar plasma chemistry. The use of ECR conditions with additional RF-biasing provides the fastest etch rates, although this produces rough surface morphologies for InP. Materials such as GaAs, AlGaAs, and GaP display smooth, stoichiometric surfaces even at the highest ECR powers employed. The etching is limited by sputter-induced desorption of the etch products for all of the III-Vs investigated.

The Raman effect in semiconductor waveguides below half‐gap is studied both experimentally and numerically. We report the depolarized Raman gain spectra up to 300 cm−1 in Al0.24Ga0.76As at pump wavelengths of 0.515 and 1.55 μm from the measurement of the absolute Raman scattering cross sections using GaAs as a reference scatterer. In addition, the coupled propagation equations for the AlGaAs waveguides are modified to include the Raman effect. By solving the coupled propagation equations numerically, we verify that the energy transfer between two orthogonally polarized pulses demonstrated in previous pump‐probe experiments [M. N. Islam et al., J. Appl. Phys. 71, 1927 (1992)] is caused by Raman effect. We also show numerically that the Raman effect induces spectral distortions on the pulses, and the energy transfer is inversely proportional to the pulse widths. The energy transfer results in a severe cross‐talk problem for sub‐picosecond pulses in AlGaAs waveguides. For example, the energy exchange is abou...

SiNx encapsulation of sulfide passivated GaAs/AlGaAs surfaces was examined with respect to the SiNx deposition conditions and applied to GaAs/AlGaAs microdisk lasers. The SiNx encapsulation is a method for preserving the positive effects (e.g., reduced surface recombination velocity, Sv) of the sulfide passivation by inhibiting the oxidation process of the air‐exposed semiconductor. GaAs‐based microdisks, with diameters of 2–10 μm, provide a very sensitive probe of the surface recombination since the resonator mode is in close proximity to the edge of the disk (∼

p‐type doping due to incorporation of carbon acceptors has proven to be extremely valuable for fabrication of various III–V device structures. In general, gaseous sources have proven to be more successful than elemental sources, with trimethylgallium and halocarbons such as carbon tetrachloride being the most commonly used intrinsic and extrinsic sources respectively. While both sources are capable of supplying carbon to the growth front, their behavior at the substrate surface is significantly different. This article will discuss how these differences affect the utility of each source for doping of various materials during growth by metalorganic molecular beam epitaxy. In particular, practical considerations such as interfacial abruptness, undesirable uptake of other impurities (i.e., hydrogen or chlorine), dependence of growth rate on dopant concentration, and incorporation efficiency will be presented.

The available plasma chemistries for dry etching of In-containing III-V semiconductors used in long wavelength laser structures have been examined with respect to suitability for fabrication of thick photonic devices. Electron cyclotron resonance discharges of CH4/H2, Hl/H2, CH3l/H2 and Cl2/CH4/H2 at low pressure (1 mTorr) and low DC bias (-100 V) were characterized for InP etch rates, selectivity for etching the semiconductor over common masking material and changes to the electrical and structural properties of the etched surface. The Cl2/CH4/H2 chemistry provided the fastest etch rates but required sample temperatures of approximately=150 degrees C and dielectric masks. Microdisk lasers were fabricated to demonstrate the suitability of this plasma chemistry to photonic device processing.

Implant isolation of thick GaAs based epitaxial structures using either multiple energy keV ions or a single MeV ion implantation is becoming more popular for devices such as heterojunction bipolar transistors or quantum well lasers. We report examples of both types of isolation schemes, using keV F+ and H+ ions, or MeV O+ ions. Post‐implant annealing at temperatures in the range 500–600 °C is needed to maximize the resistivity of the implanted material, but this causes redistribution of both F and H (but not O) and accumulation of hydrogen at strained or ion‐damaged interfaces. The amount of hydrogen motion is sufficient to cause concerns about dopant passivation occurring in the initially masked, active regions of the devices. The resistance of the ion‐implanted regions is stable for periods of ≥50 days at 200 °C, and is controlled by deep level point defects which pin the Fermi level near mid gap.

Dry etching of compound semiconductors is becoming increasingly important as design ruler shrink for electronic devices. For photonic device applications, dry or plasma etching is used fin- device isolation, fine-line pattern transfer, and fabrication of optical quality interfaces. As has been well established for Si and W. plasma etching at reduced temperatures can provide superior critical dimension control and obviate the need for operating at high bias voltages that produce excessively energetic ion bombardment t. In this work, we explore low-temperature (−60 C to +60 C) etching of the compound semiconductors GaAs, AlGaAs, and AlAs, In addition to improving etch anisotropy, which provides critical dimension control, rye find thut processing at lower temperatures improves microuniformity and reduces loading effects. At high lemperaturcs, where larger samples are observed to etch more slowly than smaller pieces (loading effect), etching rates appear limited bv reactant transport to the wafer. In this regime, both microuniformity and macrouniformity arc poor. As the temperature is reduced, the etching rate becomes limited by surfitce processes us a residue containing the semiconductor elements, etchant gases, and residual background gases forms on the surface. hi this regime, the etch rare becomes independent of surface area and uniformity is improved.

The use of carbon tetrachloride was examined as a means of suppressing deposition on the dielectric mask during the selective regrowth of III–V epitaxial layers by organometallic vapor phase epitaxy. Highly anisotropic dry etching was used to form narrow (∼1 μm wide) trenches and mesas. Reentrant mesas were formed by wet chemical etching. Under conventional growth conditions, polycrystalline GaAs was deposited over the mask adjacent to the trenches. By adding CCl4, selectivity could be greatly enhanced; however the growth rate in the trenches was significantly increased due to lateral diffusion of the reactants upon desorption from the mask thereby making acceptable control of the growth rate difficult. Addition of CCl4 during the growth of InP and AlGaAs significantly improved the selectivity in the case of growth around etched mesas.

Carbon acceptors in GaAs epitaxial layers grown from metalorganic sources are often partially passivated by hydrogen following growth. Here we examine heavily C‐doped GaAs epilayers grown by metalorganic molecular beam epitaxy and metalorganic vapor phase epitaxy by infrared absorption, secondary ion mass spectrometry, and Hall measurements. The concentration of passivated C has been determined by calibrating the intensity of infrared absorption due to C‐H complexes. We have investigated the sources of H in the layers and have found that H2 in the growth and annealing ambients is especially effective in passivating C. A brief anneal in an inert ambient at temperatures above 550 °C is sufficient to activate C acceptors that are passivated by H.

GaAs-AlGaAs quantum-well (850 nn) vertical-cavity surface-emitting lasers, with lateral current injection and shallow implanted apertures, show small signal modulation bandwidths of at least 11 GHz and large signal data rates of at least 10 Gb/s. The devices achieved a maximum output power of 2.1 mW, with a threshold current and voltage of 1 mA and 1.71 V, respectively. The shallow implantation step provides photolithographically precise aperture formation (using O/sup +/ ions), for efficient lateral current injection into the quantum-well active region of the laser, from intracavity contacts. The device aperture was 7 /spl mu/m in diameter, and the opening in the annular top contact was 13 /spl mu/m in diameter. The optical spectrum showed several transverse modes.

We relate the optical beam waist of a vertical-cavity surface-emitting laser (VCSEL) to a measurement of the transverse mode splitting found in the device's optical output spectra and to a measurement of beam divergence. We show experimentally that the results are in good agreement. Accurate knowledge of beam waists is useful for tailoring devices for single-mode or for high-speed operation and to better understand and interpret the mode spectrum.

Red emission at 621 nm from the 5 D 0 → 7 F 2 transition of Eu +3 has been obtained from GaN:Eu grown by gas-source molecular beam epitaxy. The luminescence has been found to be more intense than the red emission from metalorganic chemical vapor deposition (MOCVD) derived AlGaAs. Upon annealing in both N 2 and N 2 /H 2 mixtures up to 800°C, the integrated photoluminescence (PL) intensity was found to remain within a factor of 2 of the as grown sample. The surface morphology also remained unchanged. Thermal quenching measurements of the as-grown sample saw a reduction in the 621 nm emission of 82% as the measurement temperature was increased from 20 to 300 K. The quenching was reduced to 66% after annealing at 800°C.

In this paper HI/H{sub 2}/Ar discharges are shown to be universal etchants for III-V semiconductors, giving rise to highly anisotropic features with smooth surface morphologies. At low dc Self bias ({minus}V) and low pressure (1 mTorr), etch rates for all III-V materials of {gt}2000 {Angstrom} {center dot} min{sup {minus}1} are possible for high HI percentages in the discharges, whereas rates greater than 1 {mu}m {center dot} min{sup {minus}1} are obtained at higher pressures and dc biases. These etch rates are approximately an order of magnitude faster than for CH{sub 4}/H{sub 2}Ar mixtures under the same conditions and there is no polymer deposition on the mask or within the reactor chamber with HI/H{sub 2}/Ar. Auger electron spectroscopy reveals residue-free, stoichiometric surfaces after dry etching in this mixture. As a result, photoluminescent intensities from dry etched samples remain high with little apparent damage introduction. Changes in the near-surface carrier concentration due to hydrogen passivation effects are also negligible with HI-based mixtures in comparison to CH{sub 4}-based dry etching.

The activation kinetics and diffusion characteristics of Si+ and Be+ ions implanted into InAlAs and InGaAs were investigated for rapid thermal annealing in the temperature range 600–900 °C. The apparent activation energies for electrical activation of Be are 0.43±0.03 eV in InAlAs and 0.38±0.03 eV in InGaAs, and for Si are 0.58±0.05 eV in InAlAs and 0.64±0.06 eV in InGaAs. Higher activation efficiencies are obtained for both dopants in InGaAs relative to InAlAs and anomalously low activation for low dose Be implants is observed due to a lack of vacant sites for the Be to occupy. Extensive redistribution of Be after annealing at 750 °C, 10 s is observed in both materials, whereas Si shows no motion even for annealing at 850 °C.

We characterize the small-signal frequency response of intracavity contacted /spl sim/970 nm VCSEL's designed for flip-chip bonding to electronic circuits and then modified with reduced capacitance and a novel lateral current injection method to obtain a high-speed response. We measure 3-dB bandwidths in excess of 10 GHz and an extracted K-factor limited f-max of 95 GHz for fabricated single-mode /spl sim/970-nm lasers.

The properties of ohmic contacts to metallorganic, chemical vapour deposited In0.52Al0.48As layers are described. The Pt/Ti bilayer metallization scheme was applied to a p-type InAlAs layer (Zn-doped approximately 5*1018 cm-3) in an attempt to produce an ohmic contact. The as-deposited system exhibited rectifying behaviour with a barrier height of about 0.40 eV. Rapid thermal processing even at temperatures of 300 degrees C led to the formation of an ohmic contact. The lowest specific resistance value of 2.5*10-5 Omega cm-2 was measured for the Pt/Ti/InAlAs contact after heating at 450 degrees C for a period of 30 s. The contact microstructure was stable through heating cycles at temperatures up to 500 degrees C, above which extensive interfacial reactions were observed.

We have utilized a new aluminum source, trimethylamine alane (TMAA), in the growth of graded‐index separate‐confinement heterostructure single quantum‐well GaAs/AlGaAs laser structures by low pressure (30 Torr) organometallic vapor‐phase epitaxy. We find lower carbon and oxygen incorporation in AlGaAs epilayers using TMAA since it does not contain a direct Al–C bond and it is not susceptible to the formation of volatile Al–O containing compounds. The oxygen and carbon concentrations were below the detection limits (< 5 × 1016 cm−3 and < 3 × 1016 cm−3, respectively) of the secondary ion mass spectrometry measurements. Broad‐area lasers with 10‐nm quantum wells and Al0.45Ga0.55As cladding layers exhibited threshold current densities of 140 A cm−2 for cavity lengths of 1 mm, internal quantum efficiencies of 81%, and intrinsic losses of 1.6 cm−1. These results demonstrate that extremely high‐quality AlGaAs and GaAs quantum wells can be grown with TMAA.

The simultaneous formation of buried external collector and extrinsic base regions in GaAs/AlGaAs heterojunction bipolar transistor (HBT) structures by co‐implantation of Be+ together with O+ or H+ ions is described. Oxygen implants at doses of ≥ 1012 cm−2, or proton implants at doses ≥ 1014 cm−2, followed by annealing at 500–550 °C, create fully depleted collector regions, while similar anneals lead to significant Be activation and lowered base resistance. Higher annealing temperatures improve this Be activation but restore the initial doping level in the implanted collector region. For Be+ ion doses ≤ 5≤5× 1014 cm−2 there are no defects visible by transmission electron microscopy in the HBT structure for annealing temperatures below 800 °C.

A laser light source for high-resolution near-field optics applications with an output power exceeding 1 mW (104 times the power from previous sources) and small (300 nm square to less than 50 nm square) output beam size is demonstrated. The very-small-aperture laser (VSAL) tremendously expands the range of applications possible with near-field optics and increases the signal-to-noise ratios and data rates obtained in existing applications. As an example, 250-nm-diam marks corresponding to 7.5 Gb/in.2 storage density have been recorded and read back in reflection and transmission on a rewritable phase-change disk at 24 Mb/s with a 250-nm-square aperture VSAL. VSALs potentially enable data storage densities of over 500 Gb/in.2 (up to 100 times today’s magnetic or optical storage densities).

The effects of hydrogenation on the low‐temperature (5 K) photoluminescence properties of GaAs grown on InP substrate by metalorganic chemical vapor deposition are investigated. An emission band at ∼1.4 eV originating from the GaAs/InP interfacial region shows a 30‐fold increase in intensity relative to the GaAs band‐edge emission after exposure to hydrogen plasma for 30 min at 250 °C. This improvement in intensity is attributed to hydrogen passivation of defects at the heterointerface caused by the large (≊4%) lattice mismatch between GaAs and InP. Annealing the hydrogenated sample at 350 °C nullifies the passivation effect. Further, the 1.4‐eV band shifts to higher energy on annealing the sample in the temperature range 150–450 °C with the hydrogenated sample exhibiting a larger shift than the untreated sample. It is suggested that the annealing‐induced peak shift arises due to modification of the interface and that it is greater in the hydrogenated sample compared to the untreated sample.

Reactive ion etching (RIE) of InAs, InSB, and GaSb in either CC1{sub 2}F{sub 2}/O{sub 2} or C{sub 2}H{sub 6}/H{sub 2} discharges has been examined as a function of gas composition, flow rate, pressure, power, and etching time. The C{sub 2}H{sub 6}/H{sub 2} chemistry gives smooth, controlled etching of these materials for C{sub 2}H{sub 6} concentrations less than 40% by volume in H{sub 2}, and the etch rates are in the range 260-350 {angstrom} under these conditions. Subsurface lattice disorder was restricted to {le}50{angstrom} in depth for both types of etching. The CC1{sub 2}F{sub 2}/O{sub 2} chemistry led to consistently rougher surface morphologies on all three materials with In droplets visible on InAs. The etch rates with CC1{sub 2}F{sub 2}/O{sub 2} are higher by factors of 2-5 then for C{sub 2}H{sub 6}/H{sub 2}, and the etched surfaces all show significant concentrations of C1-containing residues.