Improvement of InGaP/GaAs heterointerface quality by controlling AsH3 flowconditions

Heterointerfaces between disordered InGaP on GaAs, whose conduction band of fset, Delta Ec, is 0.2 eV, can be improved and have less interface charges by controlling the AsH3 cover time and flow rate at the growth interval fro m GaAs to InGaP by metalorganic chemical vapor deposition. A small AsH3 cov er of 5 cc (0.05 min with 100 cc/min) creates a low interface charge densit y, sigma, of 6.4 x 10(10) cm(-2). Extending the AsH3 cover to only 25 cc in creases sigma by one order, even though AsH3 is purged by PH3 for a rather long time after being covered. Interface charges are confirmed to be donors whose energy level is near the conduction band edge. These results show th at excess As on the GaAs surface enhances the formation of donor-like defec ts in the InGaP layer. An As-poor GaAs surface is essential in order to ach ieve high-quality InGaP/GaAs heterointerfaces. (C) 1999 American Vacuum Soc iety. [S0734-211X(99)00106-7].