The effects of the SiN layer normally used to passivate and protect the exposed junction surfaces in InP/InGaAs heterojunction bipolar transistors have been studied and shown to degrade the transistor properties. These effects are ascribed primarily to surface damage associated with the high SiN deposition temperature (350 °C). A degradation of the emitter-base properties was observed through the nonideal behavior of the base current and the measured short minority-carrier lifetime in the base, extracted by using the base width modulation method. Degradation in the current gain and emitter injection efficiency was also observed. A clear recovery of the transistor was observed after removing the SiN passivation layer indicating that the high SiN deposition temperature results in a high-surface-state density which increases the surface recombination velocity and degrades the junction properties. It is concluded that a low-temperature deposition and good quality dielectric are necessary to exploit the excellent electrical properties of InP-based heterojunction bipolar transistors.

Ultraviolet (UV) absorption spectroscopy has been used to monitor the concentrations of gas-phase reactants participating in the growth of InGaAsP alloys by hydride vapor-phase epitaxy. Room-temperature absorption spectra for PH3, AsH3, and HCl as well as high-temperature (700°C) spectra of InCl, GaCl, PH3,P2, P4, As2, and As4 are presented. For the group V species, the UV absorption bands of the hydride, dimer, and tetramer exhibit considerable overlap, but can still be used to determine the approximate concentration of each species. GaCl and InCl exhibit extremely intense, sharp absorption bands at 248 and 267 nm, respectively. This technique has been used to study the effect of PH3 pyrolysis on InP growth, and to monitor In/Ga ratio for metal transport from an alloy source. This technique can be implemented on reactor systems without reactor design changes and without disturbing the thermal profile by using ‘‘light pipes’’ to probe concentrations of reactive species during growth.

The incomplete pyrolysis of PH3 is shown to have a significant effect on the growth rate and morphology of InP grown by hydride vapor phase epitaxy. Using ultraviolet absorption spectroscopy to determine the extent of PH~ pyrolysis, the growth rate of InP is shown to increase with decreasing PH~ pyrolysis. Incomplete PH3 pyrolysis is also shown to dramatically increase the formation of growth hillocks on < I00> InP epitaxia] layers. The use of various metal catalysts to expedite PH3 pyrolysis to eliminate hillock formation during InP growth is described, and a qualitative model of PH3 induced hillock growth is presented.

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This paper reports large active area (15 mm2) 4H-SiC BJTs with a low VCESAT=0.6 V at IC=20 A (JC=133 A/cm2) and an open-base breakdown voltage BVCEO=2.3 kV at T=25 °C. The corresponding room temperature specific on-resistance RSP-ON=4.5 mΩcm2 is to the authors knowledge the lowest reported value for a large area SiC BJT blocking more than 2 kV. The on-state and blocking characteristics were analyzed by device simulation and found to be in good agreement with measurements. Fast switching with VCE rise- and fall-times in the range of 20-30 ns was demonstrated for a 6 A 1200 V rated SiC BJT. It was concluded that high dynamic base currents are essential for fast switching to charge the BJT parasitic base-collector capacitance. In addition, 10 μs short-circuit capability with VCE=800 V was shown for the 1200 V BJT.