Minority-carrier lifetime measurements and defect-structure identification for gallium arsenide grown on sapphire by organometallic vapor phase epitaxy

Abstract
The minority-carrier lifetime in n-type GaAs-on-sapphire structures has been measured by transient laser-induced photoluminescence. Single- and double-heterojunction structures grown by organometallic vapor phase epitaxy have been examined and yield values of lifetime between 0.1 and 0.4 ns. Transmission and scanning electron microscopic analyses of layers show that the best surfaces and lowest defect densities resulted from isothermal growth at 690 °C. Threading dislocations in the range of 5×107 to 6×108 cm−2 are observed in GaAs grown on (0001)-oriented sapphire substrates.