Steady-state photoconductivity of gallium and indium-doped hydrogenated amorphous germanium

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

JOURNAL OF APPLIED PHYSICS

Año: 1998 vol. 83 p. 353 - 357

0021-8979

The effects of gallium and indium p-type doping on the photoconductivity of hydrogenated amorphous germanium (a-Ge:H) thin films deposited by the rf-sputtering method are reported. The quantum efficiency-mobility-lifetime (eta mu tau) product was determined at room temperature as a function of the dark Fermi energy E-F on samples with a relative dopant concentration range between approximate to 3x10(-5) and approximate to 10(-2). A decrease of eta mu tau is observed with the increase of the Ga concentration until a minimum is reached for compensated samples (E-F close to midgap level), where eta mu tau is about 16 times lower than the value obtained for intrinsic samples. This behavior is followed by an eta mu tau increase as E-F crosses the midgap level. Then, for higher Ga doping levels, eta mu tau decreases again. For In-doped samples, on the other hand, a monotonic decrease of eta mu tau is measured for all the impurity concentration range. These results are consistent with a model which assumes that the dangling bond is the main recombination path, and give independent evidence for the lack of correlation between the defect density and E-F in p-type doped a-Ge:H.