Temperature dependence of the photoconductivity of Ga-doped hydrogenated amorphous germanium films

F. T. REIS; D. COMEDI; I. CHAMBOULEYRON

JOURNAL OF NON-CRYSTALLINE SOLIDS

Año: 2000 vol. 266 p. 730 - 734

0022-3093

This work reports a study of the photoconductivity (PC) of Ga-doped a-Ge:H films as a function of temperature and photon flux. The experimental data discussed here refer to: (a) the photocurrent, Tpc, at fixed photon energy (1.3 eV) and fixed photon flux (F approximate to 2.4 x 10(16) cm(-2) s(-1)) in the 14-380 K temperature range and (b) the variation of the exponent, gamma(I-PC F-7) with temperature (55-380 K) and doping level for Fin the 8 x 10(14)-3 x 10(16) cm(-2) s(-1) range. In all cases, I-PC is approximately independent of temperature, T, in the low temperature region (T < 40 K) and increases for T > 40 K. The I-PC Of the undoped and the most lightly doped samples increases up to a maximum at T similar to 230 K, and decreases for higher temperatures (thermal quenching, TQ). The maximum peak of I-PC becomes smaller and appears as a shoulder as the doping level increases. However, this shoulder can still be interpreted as an evidence of TQ. The onset temperature of the TQ becomes smaller as the Ga concentration increases. A gamma(min), corresponding to a T-min is measured. Both gamma(min) and T-min vary with doping. The gamma(min) and T-min are maxima for compensated samples and decrease as the Fermi energy shifts from midgap in either direction.