FIELD-EFFECT ON ELECTRON-EMISSION FROM THE DEEP TI DONOR LEVEL IN INP

The effect of electric field on the thermal emission of electrons from the Ti3+/Ti4+ deep donor level in InP has been investigated. Double-correlation deep-level transient spectroscopy as well as differential-isothermal-capacitance transient measurements have been carried out on low-pressure-metalorganic-chemical-vapor-deposition-grown InP:Ti samples. It is found that the emission rates are strongly field dependent increasing by up to a factor of 17 corresponding to an increase of the field by a factor of 3.5 in the measured temperature range of 260 to 340 K. The experimental data are well fitted with a Poole-Frenkel model employing a three-dimensional square-well potential associated with the Ti3+/Ti4+ level with a radius r = 4.6 nm. The fit of this model to the experimental data yields variations in the activation energy, DELTA-E = 0.48 +/- 0.02 eV to 0.57 +/- 0.02 eV, depending upon the actual field strength. An extra-polated zero-field DELTA-E (O) = E(C)-E(T) = 0.59 +/- 0.02 eV is found. The electron-capture cross section is determined to be almost-equal-to (6.6 +/- 0.3) X 10(-13) cm2. Thus, the contraversy about the previously reported variations in DELTA-E values is resolved. A comparison of DELTA-E (0) with the Ti3+/Ti4+ energy position in GaAs and In0.53Ga0.47As shows that the energies are within 20 meV horizontally across the heterojunction, confirming a prediction of the ''internal-reference'' rule for the energy position of transition-metal levels in isoelectronic semiconductors.