TUNNEL IONIZATION OF SHALLOW ACCEPTERS AND DONORS IN GAAS

Experimental studies on shallow acceptor and donor field ionization dynamics in MBE-grown GaAs epitaxial layers are presented. The experiments have been carried out with a new non-resonant spectroscopic technique, transient tunnelling spectroscopy. It has been found that intense hole tunnelling from shallow accepters begins at electric fields higher than 6000 V cm(-1), while electron tunnelling from shallow compensating donors to the conduction band occurs at much lower electric fields, of the order of 500 V cm(-1). The dependence of the acceptor to valence band tunnelling time on the electric field strength has been measured for the first time. From the analysis of the experimental results it is concluded that initially the acceptor to valence band tunnelling dynamics is dominated by a light-hole mass.