MOVPE growth of strained InGaAsN/GaAs quantum wells

Abstract The strained In Ga As UV N V (x"0-0.01)/GaAs quantum wells (QWs) with 10 nm well thicknesses were grown by MOVPE at 500°C using dimethylhydrazine (DMHy) as the nitrogen source. The nitrogen was nonlinearly incorporated into the solid by increasing the partial pressure of DMHy in the vapor phase. The peak energy of photoluminescence (PL) was red-shifted by increasing the composition of nitrogen up to x"0.002 and showed a large band-gap bowing of !82 eV. The as-grown In Ga As N QW had a weak PL intensity of more than two orders of magnitude lower than that of In Ga As QW, but by annealing in a N atmosphere at 650°C, the PL intensity recovered and peaked at 1.26 m at 10 K. The PL recovery seems to have been related to the depassivation of hydrogen. From a SIMS analysis, the as-grown In Ga As N QW showed a hydrogen concentration as high as 6;10 cm\, but decreased to 2.5;10 cm\ after annealing in N for 1 h. 1998 Elsevier Science B.V. All rights reserved

Al2O3 Insulated-Gate Structure for AlGaN/GaN Heterostructure Field Effect Transistors Having Thin AlGaN Barrier Layers

An Al2O3 insulated-gate (IG) structure was utilized for controlling the surface potential and suppressing the gate leakage in Al0.2Ga0.8N/GaN heterostructure field effect transistors (HFETs) having thin AlGaN barrier layers (less than 10 nm). In comparison with Schottky-gate devices, the Al2O3 IG device showed successful gate control of drain current up to VGS= +4 V without leakage problems. The threshold voltage in the Al2O3 IG HFET was about -0.3 V, resulting in the quasi-normally-off mode operation

Investigation of CuGaSe2/CuInSe2 double heterojunction interfaces grown by molecular beam epitaxy

In-situ reflection high-energy electron diffraction (RHEED) observation and X-ray diffraction measurements were performed on heterojunction interfaces of CuGaSe2/CnInSe2/CuGaSe2 grown on GaAs (001) using migration-enhanced epitaxy. The streaky RHEED pattern and persistent RHEED intensity oscillations caused by the alternate deposition of migration-enhanced epitaxy sequence are observed and the growths of smooth surfaces are confirmed. RHEED observation results also confirmed constituent material interdiffusion at the heterointerface. Cross-sectional transmission electron microscopy showed a flat and abrupt heterointerface when the substrate temperature is as low as 400 °C. These have been confirmed even by X-ray diffraction and photoluminescence measurements

DC and microwave performance of AlGaN/GaN HEMTs passivated with sputtered SiNx

The effects of sputtered and room temperature plasma enhanced chemical vapour deposition (RT-PECVD) SiNx passivation on the dc and microwave performance of AlGaN/GaN high electron mobility transistors (HEMTs)are studied. The pulsed I–V characteristics from a class B quiescent bias point and transient measurements indicate that the sputtered SiNx passivation is more efficient in suppressing lag effects in AlGaN/GaN HEMTs. Dispersion-free sputtered SiNx passivated AlGaN/GaN HEMTs were obtained using this technique. Continuous-wave (CW) measurements without active cooling give a maximum output power density of 6.6 W mm−1 at Vgs=−4 V, Vds = 50 V and a maximum power added efficiency of 51.3% at Vgs=−4 V, Vds = 30 V at 3 GHz on 2 7 50 μmAlGaN/GaN HEMTs on the sapphire substrate, with a gate length of 2 μm and without field-plated gates. To the best of our knowledge, this is the highest level power density reported on the sapphire substrate without field-plate design. The extrinsic cut-off frequency ( ft) and maximumoscillation frequency ( fmax) are 51 GHz and 100 GHz, respectively, on 2 7 50 7 0.15 μm HEMTs. To our knowledge, the sputtered SiNx passivation for AlGaN/GaN HEMTs is a unique technique, which has never beenpublished before

DC and microwave performance of AlGaN/GaN HEMTs passivated with sputtered SiNx

The effects of sputtered and room temperature plasma enhanced chemical vapour deposition (RT-PECVD) SiNx passivation on the dc and microwave performance of AlGaN/GaN high electron mobility transistors (HEMTs)are studied. The pulsed I–V characteristics from a class B quiescent bias point and transient measurements indicate that the sputtered SiNx passivation is more efficient in suppressing lag effects in AlGaN/GaN HEMTs. Dispersion-free sputtered SiNx passivated AlGaN/GaN HEMTs were obtained using this technique. Continuous-wave (CW) measurements without active cooling give a maximum output power density of 6.6 W mm−1 at Vgs=−4 V, Vds = 50 V and a maximum power added efficiency of 51.3% at Vgs=−4 V, Vds = 30 V at 3 GHz on 2 7 50 μmAlGaN/GaN HEMTs on the sapphire substrate, with a gate length of 2 μm and without field-plated gates. To the best of our knowledge, this is the highest level power density reported on the sapphire substrate without field-plate design. The extrinsic cut-off frequency ( ft) and maximumoscillation frequency ( fmax) are 51 GHz and 100 GHz, respectively, on 2 7 50 7 0.15 μm HEMTs. To our knowledge, the sputtered SiNx passivation for AlGaN/GaN HEMTs is a unique technique, which has never beenpublished before