GASB/INAS HETEROJUNCTIONS GROWN BY MOVPE

We have previously reported the MOVPE growth of a GaSb/InAs heterojunction containing a two-dimensional electron gas (2DEG) in the InAs [1]. A major improvement in the electrical quality of InAs layers has subsequently resulted from the use of tertiarybutylarsine (TBAs) as the arsenic source. At 77 K, Hall mobilities and carrier concentrations were 5600 cm2/V.s and 4 x 10(15) cm-3 for GaSb and 35,000 cm2/V.s and 9 x 10(15) cm-3 for InAs. To produce these results required different growth temperatures for the two materials. The effect of varying the growth conditions for the heterojunction was studied using Shubnikov-De Haas oscillations in the transverse magnetoresistance to measure the carrier concentration in the 2DEG. This varied from 1 to 6 x 10(11) cm-2 depending on the growth conditions. Having optimised the growth conditions a series of samples were grown with InAs thicknesses varying from 200 to 2000 angstrom. These showed the transition from double heterojunction (DHET) to single quantum well (SQW) with two occupied subbands. All the samples contained a high mobility 2DEG (up to 60,000 cm2/V.s at 4 K) and the 200 and 500 angstrom SQWs also showed evidence of a two-dimensional hole gas (2DHG) in the GaSb.