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This paper critically investigates the advantages and limitations of the current-transient methods used for the study of the deep levels in GaN-based high-electron mobility transistors (HEMTs), by evaluating how the procedures adopted for measurement and data analysis can influence the results of the investigation. The article is divided in two parts within Part I. 1) We analyze how the choice of the measurement and analysis parameters (such as the voltage levels used to induce the trapping phenomena and monitor the current transients, the duration of the filling pulses, and the method used for the extrapolation of the time constants of the capture/emission processes) can influence the results of the drain current transient investigation and can provide information on the location of the trap levels responsible for current collapse. 2) We present a database of defects described in more than 60 papers on GaN technology, which can be used to extract information on the nature and origin of the trap levels responsible for current collapse in AlGaN/GaN HEMTs. Within Part II, we investigate how self-heating can modify the results of drain current transient measurements on the basis of combined experimental activity and device simulation.

We present results from GaN-based high voltage transistors used for power switching applications. The static and dynamic properties of transistors on SiC and Si substrates are determined. Overall, this technology is capable to deliver 1000 V breakdown and 95 A output current as well as a lower product of on-resistance and gate charge than conventional Si-based structures. Areas of further improvement in epitaxial growth and device processing are outlined in order to combine these high currents and high voltages in a single device.

Characterization of GaAs/Al(2)O(3) interfaces and thin (~1-10 nm) Al(2)O(3) films prepared by atomic layer deposition (ALD) is performed using variable angle spectroscopic ellipsometry (SE), x-ray photoelectron spectrometry (XPS), and stress measurements. The SE measurements reveal the presence in all samples of an interfacial layer around 1 nm-thick, though the layer originating from thermal ALD is slightly thinner than those from plasma ALD. The refractive index of the interfacial layer is found to be higher than that of a stoichiometric Al(2)O(3) film. The XPS measurements reveal higher O:Al ratios in films thinner than 4 nm, due to fact that the XPS technique probes oxygen in both the stoichiometric Al(2)O(3) films and the interfacial layers, because the mean free path length of the O1s photoelectrons is 4 nm. The perfectly symmetric Al signal in the XPS measurements suggests the absence of Al suboxides. The temperature cycle dependence of residual stress in the film reveals slightly different paths for the heating and cooling half cycles. The coefficient of thermal expansion is found to be much higher for thin films than thicker (~70 nm) films, which is attributed to the relatively large contribution of the interfacial layer to residual stress in the thin films.

Mechanical and electrical properties of Al2O3 films are compared for plasma-assisted atomic layer deposition (ALD) and thermal ALD on two substrates, GaAs and Si, of different thermal expansion coefficient. Films with stable chemical structure and mechanical residual stress could be produced by both techniques without inducing any damage to sensitive multiquantum-well structures. However, the as-deposited residual stress in the plasma ALD Al2O3 films is lower and decreases, while that in the thermal ALD films increases with the deposition temperature. Moreover, the stress hysteresis observed upon thermal cycles is much lower for the plasma ALD films compared to that for the thermal ALD films. The biaxial elastic modulus (BEM or stiffness parameter) increases with the deposition temperature for both ALD films, being higher for the plasma ALD than that for the thermal ALD at a given temperature. The higher BEM is reflected in better electrical properties of the films. Thu s, the leakage current of metal-oxide-semiconductor capacitors with the plasma ALD-Al2O3 film is three orders of magnitude lower and the breakdown voltage 20% higher than that of the capacitors with the thermal ALD film.

In this paper a Gallium Nitride MMIC technology for RF- and microwave and high power amplifiers based on 100 nm gate technology is presented. The MMIC technology includes alloyed ohmic contacts, T-shaped 100 nm gates, air-bridges, MIM capacitors, inductors, and a full through wafer viahole backside process. As a key element for a high MMIC yield, we'll present low ohmic contact resistances with a high yield on several wafers in different processing batches and low leakage currents for a reliable device performance, respectively. Single HEMT performance exhibits PAE values of up to 60 % and power densities of 1.3 W/mm. For a single stage power amplifier with a WG = 4×45 µm dual-gate HEMT configuration, a gain beyond 10 dB at 60 GHz is presented. By using only one transistor for the amplifier stage, a maximum output power of more than 21 dBm and a PAE of 9.3% is achieved.

We report on the trade-off between performance and reliability for AlGaN/GaN transistors. It is shown that changes in epitaxial growth, transistor design and process may lead to an improvement in performance but are, at the same time, accompanied by a degradation of device reliability. As a result we show strategies in order to balance performance and reliability as both are linked. Based on these findings we have realized state-of-the-art power bars for mobile communication systems and X-band MMICs for radar applications.

In this work we systematically study the structural, optical and electrical properties of AlGaN/GaN heterostructures grown by MOCVD 3-inch on SiC substrates Thefinally developed HEMTs demonstrate excellent highvoltage stability, high power performance and large power added efficiencies. For a drain bias of 100 V an output-power-density around 26 W/mm with 25 dB linear gain is obtained. On 36 mm gate width devices an output power beyond 100 W is achieved with a power added efficiency above 60% and a linear gain around 17 dB. Ruggedness on these large devices is proven by successfully passing harsh intentional device mismatch tests during operation at 50 V. Reliability is tested at a drain bias of 50 V. Under DC conditions a drain-current degradation below 20% after 20 years is extrapolated. Under RF stress the observed change in output power is well below 0.1 dB after a test duration of more than 500h.

The design, realization, and characterization of highly efficient powerbars and monolithic microwave integrated circuit (MMIC) high-power amplifiers (HPAs) with AlGaN/GaN high electronic mobility transistors (HEMTs) are presented for the frequency range between 1 and 30 GHz. Packaged powerbars for the frequency range between 1 and 6 GHz have been developed based on a process called GaN50 with a gate length of 0.5 mm. Based on a GaN25 process with a gate length of 0.25 mm, high-power MMIC amplifiers are presented starting from 6 GHz up to advanced X-band amplifiers and robust LNAs in microstrip transmission line technology.

Based on metamorphic InAlAs/InGaAs HEMTs on 4" GaAs substrates, advanced integrated circuits for millimeter-wave applications were realized. An extrinsic transit frequency of 410 GHz for 50 nm gate length devices is achieved. The IC process features high yield on both transistor and circuit levels. Two-stage low-noise amplifiers demonstrate a small signal gain of 20 dB and a noise figure of 2.4 dB at 94 GHz. An amplifier MMIC developed for G-band operation exhibits a gain of 21 dB at 220 GHz. These results are very competitive to those achieved using state-of-the-art InP-based HEMT technologies

High-power 1.91-µm (AlGaIn)(AsSb) quantum-well diode laser single emitters and linear arrays with improved waveguide design were fabricated and characterized. The use of a rather narrow waveguide core results in a remarkable low fast axis beam divergence of 44 deg full-width at half-maximum. For single emitters, a continuous-wave (CW) output power of nearly 2 W has been observed. We have achieved 16.9 W in CW mode at a heat sink temperature of 20 deg C. The efficiencies of more than 25% are among the highest values reported so far for GaSb-based diode lasers, and allow the use of passively cooled and, thus, less expensive heat sink technologies.

High-power high-brightness 1.93-µm wavelength (AlGaIn)(AsSb) tapered diode lasers with a narrow vertical waveguide design are reported for the first time. A nearly diffraction-limited continuous-wave output power of 1.5 W together with a remarkable low fast axis divergence of 43° full-width at half-maximum have been demonstrated. The maximum brightness amounts to 32 MW/cm2 sr.

High-efficiency tapered diode lasers with ridge-waveguide structure emitting at 976 nm have been realised. High wall-plug efficiencies of more than 57% result in output powers of more than 12 W for a single emitter with 3.5 mm resonator length. A nearly diffraction limited behaviour has been demonstrated up to 8.3 W CW.

In this paper, we report the achieved performance of devices and integrated circuits (ICs) using a manufacturable InP DHBT-based technology.High speed MBE grown InGaAs/InP DHBTs with an effective emitter junction area of 4.8 µm2 exhibited peak fT and fMAX values of265and305GHz, respectively, at a collector currentdensity of 3.75 mA/µm2. Using this technology, a set of basic analog and digital IC building blocks,including lumped amplifiers, voltage controlled oscillators, multiplexers and demultiplexers, suitable for operation at 40 Gb/s and beyond, have been successfully designed and fabricated.

In this paper the MMIC technology, design and characterization of a high power amplifier and driver amplifier MMIC at 30 GHz in AlGaN/GaN HEMT technol-ogy are presented. The MMICs are designed using CPW technology on a 390 µm thick SiC substrate. The measured small-signal gain of the driver is 14 dB at 28.5 GHz and the measured output power is 28.6 dBm at 28 GHz. The power amplifier shows a measured small-signal gain of 10.7 dB at 25.5 GHz and output power of 34.1 dBm at 27 GHz. Both MMICs have a very good yield and performance for a first iteration design.

A two-stage high-power amplifier MMIC was realized with a chip size of 4.5 mm x3 mm operating between 8GHz and 10 GHz based on a fully integrated microstrip AlGaN/GaN HEMTtechnology on s.i. SiCsubstrate.TheMMIC device delivers a maximum pulsed out put power of 8.9 W (39.5 dBm) at 8.5 GHz at VDS = 31 V,10%dutycycle,and more than 6 dB gain compression level, and features a linear gain in excess of 20 dB.

The long-term stability of a 50 nm low-noise metamorphic HEMT technology has been investigated by biased accelerated lifetime tests on both MHEMT devices and two-stage LNAs for W-band applications. The lifetime tests were performed at three channel temperatures, a drain voltage of 1 V and a power density of 0.3 W/mm in air. Based on a -10% degradation of g(ind m max) failure criterion an activation energy of 1.6 eV and a projected median lifetime of 2.7 x 10(exp 6) h at T(ind ch) =125 deg C were determined. The two-stage LNAs were stressed at a channel temperature of 185 deg C for 4000 h. The S-parameters did not show any significant degradation after 4000 h of stress time if the positive threshold voltage shift was compensated for by a corresponding increase of the gate voltage. The reliability results demonstrate the stable operation of 50 nm MHEMTs and LNAs for W-band applications and beyond.

This work presents MMIC low-noise amplifiers based on AlGaN/GaN HEMT technology on SiC substrate for robust receiver applications at X-band between 8 GHz and 11 GHz. Three versions of one-stage and two versions of two-stage amplifiers are presented with a noise figure of 1.81 dB at 10 GHz and 18 dB of small-signal gain for the two-stage device fully integrated in coplanar passive technology. The paper describes modeling and circuit design, bias dependence of the small-signal and noise circuit parameters of the MMICs realized, and highpower and intermodulation behavior.

The lifetime of InGaAs/AlGaAs high power lasers increased significantly when silicon nitride (SiN) films deposited using electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) technique were used as optical coatings for the emitting facet of the lasers. Precleaning of the surfaces to be coated, and the stable low stress in the film have been found to be highly valuable for these lasers. The films were deposited at a low temperature (90°C) from a mixture of Ar, N2, and SiH4 as precursors. Rutherford backscattering spectroscopy and nuclear reaction analysis measurements reveal that the composition of the film is 48 atom % Si, 32 atom % N, and 20 atom % H. The most important properties of the films are low intrinsic stress and a negligible hysteresis in the dependence of stress on temperature upon thermal cycling. The stress measurements indicate that all hydrogen atoms in the films are chemically bonded.

At 1 x 12 metal-semiconductor-metal (MSM) photodiode array operating at 10 Gbit/s per channel was developed for short-haul 0.85 µm wavelength parallel optical links. The GaAs-based MSM photodiodes with a diameter of 80 µm have a responsivity of 0.30 A/W a 3 V, a dark current of less than 1 nA at 3 V, a capacitance of 0.20 pF at 1 MHz, and a - 3 dB bandwidth of 10 GHz at (2.5 V, 50 Ohm).

DBR-laser diodes are very interesting light sources due to their narrow linewidth, frequency stability and large sidermode suppression. They are suitable for monolithic integration, which makes them a very attractive light source for monolithic master oscillator power amplifier devices.