GSMBE growth of GaAs at low AsH 3 cracking temperatures

Abstract

A series of nominally undoped GaAs layers were grown by gas source MBE (GSMBE) with an elemental Ga source and AsH 3 cracked by a low pressure Ta gas cracker at cracking temperatures, T gas, between 500 and 1100°C. For T gas below 800°C the AsH 3 flow rate was increased to maintain an As-stabilized surface. All samples were found to be p-type. The net carrier concentrations decreased linearly as T gas was decreased from 800 to 500°C; for T gas =800° C, μ 77 K =4300 cm 2/ V⋯ s, whereas when T gas=500°C, μ 77K=6400 cm 2/V⋯s. Low temperature photoluminescence (PL) on samples grown at T gas =900° C and T gas =500° C showed carbon to be the dominant acceptor and a much lower level of carbon incorporation at the lower gas cracking temperature. Quadrupole mass spectrometer measurements of the AsH 3 pyrolysis by the gas cell indicate only partial cracking occurring for T gas =500 to 800°C; thus, AsH 3 fragments may be affecting carbon incorporation at the growth surface.