Masakiyo Ikeda

Uniform growth of GaAs by MOCVD on multi-wafers

Abstract The thickness of the stagnant layer observed by smoke gas simulator is correlated to that of the epitaxial layer of GaAs. With this knowledge we developed an atmospheric pressure MOCVD system with a barrel reactor for large area epitaxial growth of GaAs and GaAlAs. The susceptor is a hexagonal frustum in shape, on which six 2 inch diameter wafers are set. It was known that the tapering angle of the susceptor and the number of its revolutions affect uniformity in the thickness of epitaxial layer. Under the optimized growth conditions, variation of layer thickness in a wafer was less than ± 5%. Variation of average layer thickness of a wafer was less than ± 2% in a run and that of six wafers in a run was less than ±2% from run to run. In S-doping by using H 2 S, the uniformity of carrier concentration depended on growth temperature and [AsH 3 ]/[TMGa] ratio. Under the optimized growth conditions, variation of the carrier concentration in a wafer, the average carrier concentration of a wafer in a run and that of six wafers in a run from run to run were less than ±5%.

AIGaAs/GaAs Heterojunction Bipolar Transistors with C-Doped Base Grown by AP-MOVPE

Abstract C-doped GaAs layers were grown by the atmospheric pressure metalorganic vapor phase epitaxy (AP-MOVPE) method using TMGa and TMAs at low temperature and low V/III ratio. Carbon concentrations up to 7 × 10 19 cm −3 were obtained, and their mobility was higher than for Zn-doped GaAs. Using this C-doped GaAs as the base layer, AlGaAs/GaAs HBTs were fabricated, and current gain up to 50 was demonstrated for the sample with a base layer of 700 A in thickness and 4 × 10 19 cm -3 in concentration. The uniformity across the wafer and the reproducibility of the current gains were considered to be good enough for the use of this epitaxial layers as HBT ICs.

Performance comparison of metalorganic vapor phase epitaxy grown C-doped GaAs/AlGaAs heterojunction bipolar transistor wafers between AsH3 and trimethylarsenic for the base layer growth

C-doped GaAs layers were grown with AsH 3 and As trimethylarsenic (TMAs) for the As source by a production scale metalorganic vapor phase epitaxy machine. In both cases, highly (p = (1-4) × 10 19 cm −3 ) p-type C-doped GaAs layers were grown and no significant difference in their mobilities, carbon activation ratios and electron lifetimes were observed. By means of these methods, GaAs/AlGaAs heterojunction bipolar transistor (HBT) layers were grown and HBT test devices were fabricated. Current gains up to the base layer concentration of 3 × 10 19 cm −3 were almost equal for these two methods, but at a concentration of p = 4 × 10 19 cm −3 , the current gain of HBT whose base layer was grown with AsH 3 decreased rapidly. On the other hand, a current gain as high as 100 was demonstrated for a HBT whose base layer was grown with TMAs and was 4 × 10 19 cm −3 in concentration

In-doped GaAs substrate assessment for thin film applications

Abstract We have evaluated In-doped GaAs from the viewpoint of its use as a substrate for the growth of MOCVD and MBE epitaxial layers. The distribution of misfit dislocations at the undoped GaAs epilayer/In-doped GaAs substrate interface was assessed with X-ray topography and correlated with surface morphology. No significant difference was found in the critical thickness for generating misfit dislocations between the MOCVD and MBE growth method. The stress distribution in samples with misfit dislocations was revealed in their birefringence patterns. The out-diffusion of indium from the substrate to the epilayer was observed in neither MBE nor MOCVD GaAs epilayer growth.