S.G. Hummel

GaAs-based opto-thyristor for pulsed power applications

An optically gated, GaAs bipolar junction thyristor with a semi-insulating base layer, specifically developed for pulsed power applications, is reported, and initial device performance characteristics as a pulsed power switch are presented. The measured DC blocking voltage of the device was >600 V, peak pulsed current was >or=70 A, and the current rise rate was >1.4*10/sup 9/ A/s. These results demonstrate that GaAs based junction devices have significant potential as switching elements for pulsed power systems requiring very fast closing times. >

Use of tertiarybutylarsine in the fabrication of GaAs/AlGaAs quantum wells and quantum well lasers

Tertiarybutylarsine was used in the growth of GaAs and AlGaAs by metalorganic chemical vapor deposition over a range of compositions and V/III ratios. GaAs layers were obtained with both n‐ and p‐type background carrier concentrations in the low 1014 cm−3 range. AlGaAs was grown at 20, 30, and 50% compositions, and photoluminescence of the Al0.2Ga0.8As indicates high quality material with full width half maximum (FWHM) values of the peaks being comparable to arsine‐grown AlGaAs. High quality multiple Al0.3Ga0.7As/GaAs quantum wells of various widths produced photoluminescence spectra with FWHM values comparable to arsine‐grown samples. Minority‐carrier lifetimes as long as 400 ns were measured for a heterostructure of 0.5 μm GaAs with Al0.3Ga0.7As barrier layers. Graded index separate confinement heterostructure lasers were fabricated, and broad‐ area test results of these devices produced threshold current densities as low as 186 A/cm2.

Optimization of stripe width for low-threshold operation of quantum well laser diodes

An experimentally verified model for threshold current in GaAs/AlGaAs quantum well laser diodes has been extended to calculate for the first time the dependence of threshold current on stripe width. The lowest possible threshold is shown to occur when the lateral confinement factor is in the range of 55–60% for typical devices, a value that is not affected by mirror reflectivity or lateral index step. A simple, generalized optimization scheme for obtaining the unique width/length combination that results in lowest threshold is presented, and predicts potential as‐cleaved threshold currents as low as 0.5 mA.

Characteristics of GaAs, AlGaAs, and InGaAs materials grown by metalorganic chemical vapor deposition using an on-demand hydride gas generator

We report results on the properties of GaAs, AlGaAs, and InGaAs materials grown using a new, on‐demand hydride gas generator. Low pressure arsine gas is generated from an arsenic containing precursor (KAsH2) by the controlled addition of water as a chemical activator. Both generated and bottled arsine are used to grow GaAs, AlGaAs, and InGaAs structures using atmospheric pressure metalorganic chemical vapor deposition. Using generated arsine, GaAs layers with background carrier concentrations of less than n=3×1013 cm−3 were produced across a growth temperature range of 625–725 °C using a V/III ratio of 30. InGaAs grown at 640 °C with V/III=30 exhibits a background carrier concentration of n=2.5×1014 cm−3 and mobility values of μ300 K=11 350 cm2/V s and μ77 K=71 200 cm2/V s. Photoluminescence measurements show highly resolved exciton spectra using either generated or bottled arsine with donor‐bound exciton linewidths as narrow as 0.16 meV full width at half‐maximum. Broad area GaAs/AlGaAs laser devices exh...

GaAs opto-thyristor for pulsed power applications

An optically gated thyristor based on GaAs has been designed fabricated and investigated for pulsed power applications. The device included a 200-pm semi-insulating base layer and was triggered with an 848-nm 1-pJ 100-nsec laser diode. The DC blocking voltage of the thyristor was observed to be V the peak current 300 A and the current rate of rise A/sec. Lock-on effect was also observed and is discussed.

Advanced epitaxial techniques for optoelectronic devices

High speed interconnection networks, local area networks, and optical recording systems require high density linear arrays of individually addressable lasers. A practical implementation of injection lasers in these applications requires that the lasers have ultralow threshold (<1 mA), high differential quantum efficiency (80%), and high yield. These specifications exceed what is currently possible in an integrated array of the type required. Although low threshold lasers with high differential quantum efficiency have been fabricated,1 the processes typically employed are not amenable to high yield integrated devices, and no work has yet addressed the problems associated with crosstalk (electrical and optical) in such arrays.

High speed static induction transistor for pulsed power applications

The proposed design and fabrication of a recessed-gate GaAs static induction transistor (SIT) are reported. The SIT is a vertical channel, field-effect switching device which exhibits gate-induced turn-on and turn-off and is well-suited for pulsed power applications. Modeling of the device has been performed to correlate the experimentally observed characteristics with calculated values upon fabrication. The base (channel) layer is grown by vapor phase epitaxy, and the dopant concentration and thickness of this layer are designed to achieve optimum device characteristics. The current risetime in the SIT is limited by the rate of decrease of the potential barrier in the channel as well as the transit time of carriers from the source to the drain region of the device. In this case, assuming that electrons travel across the drift region at saturation velocity, the transit time is calculated to be <500 ps.<<ETX>>