Field induced carrier capture and optical release from traps in highly doped GaAs:Si

Abstract

Carrier capture induced by electric fields in δ-like GaAs highly doped with Si is investigated with respect to the carrier heating necessary for such a charge transfer and the energy required to release the trapped carriers. The existence of a threshold field is established. The value of the threshold field for capture is in accordance with either trapping via the L band or a process that is direct but assisted by a large-wavevector phonon. The release of the carriers from the metastable traps due to infrared excitation, measured in terms of its dependence on the wavelength, yields a significantly higher threshold than is usually required for thermal excitation. This indicates the substantial lattice relaxation involved to form the charged trap.

A new channel of phonon emission induced by metastable centres of highly planar-doped GaAs:Si

“…Above the threshold field for the formation of metastable centres such a sequence of pulses already influences the sample during the ToF measurement. In order to diminish the accumulation of centres in such experiments, when measuring the initial current-voltage characteristic, prior to the application of each subsequent field strength the sample was illuminated [2]. In this way the systematic error was reduced for this 'initial state'.…”

“…In heavily planar-doped GaAs:Si the capture of hot electrons in the process of formation of metastable centres was demonstrated by a current decrease [1]. It was shown that the current change depends on field strength and tends to saturate with a characteristic time of 10 −3 to 10 −4 s. The capture effect only becomes implemented at field strengths above a threshold of a few kV cm −1 (depending on the doping level) [2]. The existence of a threshold demonstrates that the electron energy itself is not the critical parameter since there is always a continuously increasing number of high energy carriers in the tail of the distribution with increasing field strength.…”