CARRIER DYNAMICS AND PHOTODETECTION IN CHARGE INJECTION TRANSISTORS

We study picosecond carrier transport dynamics induced by 200 fs 1.55 mu m optical pulses in charge injection transistor structures. We prop ose and demonstrate a new optoelectronic method for exploring the inte ractions of hot majority carriers and cold minority carriers, as well as the optical control of real space transfer in these devices. The mi nority holes photogenerated in the channel produce substantial cooling of the hot-electron majority carriers and lead to the reduction of th e real space transfer. The new method also provides a direct measure o f the minority carrier lifetime in the transistor channel. These effec ts are demonstrated in InGaAs-channel devices with both InAlAs and InP barriers. The similarities in the device characteristics are explaine d in terms of the interaction of photogenerated minority holes with ma jority electrons in the channel leading to a photoconductor-like drain current and to a reduction in the real space transfer collector curre nt. The differences are attributed to the different conduction and val ence band energy offsets between the wide band gap barrier and the low band gap collector and channel layers. Furthermore, the InAlAs-barrie r device shows a capability of serving as a practical photodetector wi th the measured, system-limited recovery speed of similar to 5 ps. (C) 1996 American Institute of Physics.