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The isochronal and isothermal annealing characteristics of acceptor‐doped GaAs:Be grown at low substrate temperatures (300 °C) by molecular‐beam epitaxy (LTMBE) have been studied. The Be was introduced in a range of concentrations from 1016 to 1019 cm−3. Electrical measurements of as‐grown material up to the highest Be concentration of 1019 cm−3 show that no free holes are contributed to the valence band even though Raman spectroscopy of the Be local vibrational mode indicates that the majority of the Be impurities occupy substitutional sites. It is proposed that Be acceptors are rendered inactive by the high concentration of AsGa‐related native donor defects present in LTMBE material. The concentration of AsGa‐related defects in the neutral charge state was estimated from infrared absorption measurements to be as high as 3×1019 cm−3. A distinct annealing stage at 500 °C, similar to that found in irradiation‐damaged and plastically deformed GaAs, marks a rapid decrease in the concentration of AsGa‐related...

A wavelength-tunable actively mode-locked erbium fiber ring laser was demonstrated using a Fabry–Perot semiconductor modulator. The modulator played the simultaneous roles of an intensity mode locker and a tunable optical filter. Stable single- or dual-wavelength nearly transform-limited picosecond pulses at gigabit repetition rates were generated. Continuous wavelength tuning was achieved by simply controlling the temperature of the modulator. Pulse train with a repetition rate up to 19.93 GHz (eight times the driving frequency) was obtained by using rational harmonic mode-locking technique.

We present a highly sensitive fiber temperature sensor based on a gain-switched Fabry–Perot semiconductor laser self-seeded from a linearly chirped fiber Bragg grating. A temperature resolution of better than 0.1 °C was demonstrated. This sensor not only has the advantage of robustness against fluctuating light levels, but also obviates the need for fine wavelength discrimination.

Electrical single- and dual-wavelength tuning and three-wavelength operation of an actively mode-locked fiber ring laser generating picosecond pulses were demonstrated by using a cavity with large dispersion. A continuous tuning range up to ∼37 nm of single-wavelength picosecond pulses at ∼1 GHz was achieved by only changing the modulation frequency. Continuous wavelength tuning of dual-wavelength (18.5 nm spacing) 3 GHz picosecond pulses was also demonstrated with a tuning range up to ∼17 nm. The tuning ranges were mainly limited by the gain bandwidth of the Er-doped fiber. Simultaneous generation of three-wavelength picosecond pulses at ∼2 GHz was also demonstrated by further increasing the cavity dispersion.

Secondary‐ion mass spectrometry has been used to analyze the Al and In depth profiles in pseudomorphic GaAs/InGaAs/AlGaAs modulation‐doped field‐effect transistor structures. Surface segregation of In was found on the upper interface of the strained InGaAs layer under a moderate growth temperature of 510 °C. The segregation effect was found to be suppressed when the As4 overpressure was doubled. Ion channeling measurements are capable of differentiating the coherency of the strained InGaAs layer in the samples studied. A correlation was found between the coherency of the layer and its electrical transport property.

Strained GaAs/InGaAs/AlGaAs quantum well structures have been grown by molecular beam epitaxy at substrate temperatures from 375 to 510 °C. The well layer thickness and In composition are analyzed by ion channeling and particle‐induced x‐ray emission as a function of growth temperature. Test structures for modulation‐doped field‐effect transistors grown at 375 and 510 °C under two different As4 overpressures were also characterized by Van der Pauw measurements and low‐temperature photoluminescence. The observed differences in film quality can be explained by the influence of substrate temperature and As4 flux on the cation surface mobility during growth of the InGaAs layer.

We have investigated strained InGaAs single quantum well structures using MeV ion beam methods. The structural properties of these structures, including composition and well size, have been studied. It has been found that the composition obtained by Rutherford backscattering spectrometry and particle‐induced x‐ray emission techniques agrees very well with that obtained by the ion channeling method.

The growth of unintentionally doped indium phosphide by low pressure metalorganic chemical vapor deposition (LPMOCVD) using triethlylindium and phosphine has been investigated by low temperature photoluminescence (PL). Pregrowth annealing was found to result in improved crystalline quality of the seed surface. The predominant acceptor impurity on the annealed substrate surface and in the initial epitaxial region (1200 A) was shown to be carbon. The major acceptor impurity in thicker epilayers further away from the substrate interface was determined to be Zn. Silicon was also identified from the PL spectra, though its concentration might be much smaller than that of zinc. No deep level impurities were observed in this material. Most important of all, the highly resolved exciton PL spectrum demonstrated that excellent quality InP comparable to the best material grown by vapor phase epitaxy could be grown by LPMOCVD without the need for phosphine cracking.

High‐quality modulation doped In0.53Ga0.47As/InP heterostructures have been grown by atmospheric pressure metalorganic chemical‐vapor deposition (MOCVD) using solid trimethylindium source. The two‐dimensional nature of electrons bound in the In0.53Ga0.47As/InP heterojunctions is proved by a Shubnikov‐de Haas effect experiment. Electron Hall mobilities as high as 12000, 83000, 98000, and 92000 cm2/V s at 300, 77, 40, and 4.2 K are obtained, respectively. The electron effective mass is measured to be m*CR =0.043 m0 by cyclotron resonance experiments on the samples with two‐dimensional electron sheet concentrations of (3.0–3.7)×1011/cm2. From far‐infrared impurity absorption data the ionization energy of the residual donors in the MOCVD‐grown In0.53Ga0.47As is determined to be 2.95 meV.

We have found a new electron trap state in Si‐doped AlxGa1−xAs by deep level transient spectroscopy and constant temperature capacitance transient measurements under strong light illumination. This new trap is shallower than the DX center associated with Si impurity in that its emission and capture activation energies are equal to 0.20±0.05 and 0.17±0.05 eV, respectively. Its maximum concentration is comparable to the concentration of the DX center. Possible origins of this new trap and its relationship to the DX center are discussed.

The uninterrupted growth of high quality GaInAs layers on InP buffers by atmospheric pressure metalorganic chemical vapor deposition using trimethylindium is reported. A lattice mismatch smaller than 4.3×10−4 and low‐temperature photoluminescence exciton linewidth of 2.6 meV have been obtained, along with best 300‐K, 77‐K, and 4.2‐K Hall mobilities of 11 200, 64 000, and 80 000 cm2/Vs, respectively. Such high mobility values at 4.2 K are explained by the existence of a two‐dimensional electron gas and demonstrate the superior quality of the GaInAs epilayers grown in our laboratory.

Growth of very high quality unintentionally doped InP by low pressure metalorganic vapor phase epitaxy using solid trimethylindium as the indium source is described. Hall mobilities of 5370 cm2/Vs (300 K) and 131 600 cm2/Vs (77 K) with residual carrier concentration of 2.5×1014 cm−3 have been obtained. Low‐temperature photoluminescence exciton spectra revealed that the neutral acceptor‐bound‐exciton emission was hardly observable, indicating a very low compensation ratio.