Recombination processes in doubly capped antimonide-based quaternary thin films

Recombination processes in antimonide-based materials for thermophotovoltai c (TPV) devices have been investigated using a radio-frequency (rf) photore flectance technique, in which a Nd-YAG pulsed laser is used to excite exces s carriers, and the short-pulse response and photoconductivity decay are mo nitored with an inductively coupled noncontacting rf probe. Both lattice-ma tched AlGaAsSb and GaSb have been used to double cap InGaAsSb active layers to evaluate bulk lifetime and surface recombination velocity with differen t active layer thicknesses. With an active layer doping of 2 X 10(17) cm(-3 ), effective bulk lifetimes of 95 ns and surface recombination velocities o f 1900 cm/s have been obtained. As the laser intensity is increased the lif etime decreases, which is attributed to radiative recombination under these high-level injection conditions. Similar measurements have been taken on b oth TPV device structures and starting substrate materials for comparison p urposes. (C) 1999 American Institute of Physics. [S0021-8979(99)08715-0].