YG(张永刚）) Zhang

Comparison of thermal characteristics of antimonide and phosphide MQW lasers

The thermal characteristics of antimonide ridge waveguide MQW lasers have been investigated numerically and experimentally, and compared with phosphide lasers in detail. Using the finite-element method, the heat accumulation and dissipation process of the lasers under CW and pulse driving conditions have been simulated, and quantitative thermal time constants were introduced to describe the cooling efficiency of the lasers. The non-uniform temperature distribution inside the active core of the laser and its effects on lasing spectra have been discussed, and confirmed by the measurement of the broadening of the lasing spectrum towards the blue side. A way to improve the thermal property of antimonide lasers have also been proposed and discussed.

Characterization of InAlAs/InGaAs/InP mid-infrared quantum cascade lasers

A mid-infrared laser characterization system, including a GPIB programmable I-P and I-V set-up based on direct waveform measurement with extraordinary wide pulse duration and duty cycle tuning range, in conjunction with a Fourier transform infrared spectroscopy system adapted with double modulation technique, has been developed. Based on this characterization system, the characteristics of gas source MBE grown InAlAs/InGaAs/InP quantum cascade lasers (QCL), especially their thermal property, have been evaluated. The results show that in the combination of I-P, I-V and spectral measurements at various driving pulse parameters, the thermal resistance, lasing conditions as well as spectral characteristics of the mid-infrared QCL could be deduced. This characterization system is also a useful tool for the evaluation of other types of diode lasers in the mid-infrared band.

Metal-semiconductor-metal ultraviolet photodetectors using 6H-SiC

Metal-semiconductor-metal (MSM) UV photodetectors on n-type 6H-SiC epitaxial wafers have been reported for the first time, in which no p-n junctions or ohmic contacts are needed. Peak response wavelength at 340 nm and dark current of 1 pA at 20-V bias voltage have been measured. The photodetectors also show fair response to 193-nm wavelength deep UV light.

The effect of dispersion of the refractive index on the performance of mid-infrared quantum cascade lasers

In this paper, we present the results of the calculation and design for waveguide and the dependence on the performance of mid-infrared InAlAs/InGaAs/InP quantum cascade (QC) lasers grown by gas source molecular beam epitaxy. The dispersion of refractive indices are calculated by taking into account the contribution of the free-carrier concentration absorption. We also report the first GSMBE grown InAlAs/InGaAs/InP QC lasers emitting at 5.1mm, operated in pulse mode up to 130 K with T0 of 208 K and J0 of 2.6 kA/cm 2 . For the QC laser designed with lower waveguide cladding InP concentration of 1 � 10 18 cm � 3 , it does not lase. Presented theoretical and experimental results indicate that the free-carrier absorption in both upper InGaAs contact layer and lower InP waveguide cladding does play an important role in the dispersion of the index of refraction of semiconductors at mid–far-infrared wavelengths and influence the performance of QC lasers. # 2001 Elsevier Science B.V. All rights reserved.

AlInP-GaInP-GaAs UV-enhanced photovoltaic detectors grown by gas source MBE

Al/sub 0.52/In/sub 0.48/P-Ga/sub 0.51/In/sub 0.49/P-GaAs photovoltaic detectors using GaInP as the light absorption layer and AlInP as the widow layer have been fabricated by using gas source molecular beam epitaxy, and their performance has been characterized in detail. The detectors show infrared-blind and ultraviolet-enhanced features and have good response in visible band, which makes them a good candidate in certain applications. Excellent performance has been demonstrated on the detectors, a resistance area product of R/sub 0/A=1.3/spl times/10/sup 8/ /spl Omega//spl middot/cm/sup 2/, and an open-circuit voltage of V/sub oc/>1.05 V have been measured at room temperature.

Improved performance of InAlAs-InGaAs-InP MSM photodetectors with graded superlattice structure grown by gas source MBE

We report on the improved performance of InAlAs-InGaAs-InP metal-semiconductor-metal photodetectors (MSMPDs) with graded superlattice structure grown by gas source molecular beam epitaxy. Low dark current density of 0.75 pA//spl mu/m/sup 2/ at 10-V bias, high-breakdown voltage of >40 V at 10 /spl mu/A and fast transient response of /spl sim/16 ps (t/sub r/, FWHM and t/sub f/) at 5-V bias have been obtained.

Characterization of GaN grown by RF plasma MBE

Abstract GaN (Gallium nitride) has been grown successfully on sapphire by RF plasma MBE through optimizing the growth condition. Two dimensional triple axis mapping (TDTAM) was used to characterize the GaN epilayers. The dislocation density in the epilayers was estimated to be about 7.8×108 cm−2 according to the mosaic model. The 77K photoluminescence (PL) of the Si-doped GaN with different concentration show that Si can act both donor and acceptor at very high concentration. Transmission spectrum has also been measured for further understanding of the sample.

BCl3/Ar ICP Etching of GaSb and Related Materials for Quaternary Antimonide Laser Diodes

Inductively coupled plasma (ICP) etching of GaSb, AlGaAsSb, and InGaAsSb using BCl 3 /Ar plasma discharges was investigated for the fabrication of GaInAsSb/AlGaAsSb/GaSb laser diodes. Etching rates and selectivity were characterized as functions of gas flow ratio, accelerating voltage, and ICP source power, and the etching mechanism was discussed in detail. It is observed that the etch rate of GaSb and AlGaAsSb is much higher than that of InGaAsSb. The etched surfaces of GaSb, AlGaAsSb all have comparable root-mean-square roughness to the unetched samples over a wide range of plasma conditions; however, it is much rougher in etching of InGaAsSb. The selectivity between GaSb and AlGaAsSb was close to unity over the entire range of plasma conditions investigated, which is desirable for the fabrication of quaternary antimonide laser diodes.

Room Temperature Low-Threshold Mid-Infrared Quantum Cascade Lasers

We report room temperature low current density of InP-based AlInAs/InGaAs quantum cascade laser (QCL). For a 7.66-mum QCL, the threshold current density of 1.7 kA/cm2 at 300 K, pulsed output power of 800 mW at 80 K, and continuous-wave (CW) output power of 13 mW at 135 K are achieved. An 8.91-mum QCL comprised 100 stage active region operating up to 320 K in pulsed mode also presented.