Hall Mobility of Optically Excited Carriers in Germanium

Abstract

Steady-state Hall coefficient measurements of optically excited carriers have been made for high-resistivity gold-, iron-, cobalt-, and nickel-doped germanium crystals in the temperature range from 200\ifmmode^\circ\else\textdegree\fi{}K to 54\ifmmode^\circ\else\textdegree\fi{}K. In the spectral region of impurity absorption, ($h\ensuremath{\nu}<0.7$ ev), carriers generated in $p$-type samples are holes; carriers generated in $n$-type samples are electrons. In the region of intrinsic absorption, ($h\ensuremath{\nu}>0.7$ ev), Hall coefficient measurements indicate that photoconduction is due primarily to mobile electrons in both $p$- and $n$-type high-resistivity samples. These observations suggest that, in the crystals studied, hole trapping is primarily responsible for the intrinsic photosensitivity in both $n$- and $p$-type samples. These results are qualitatively consistent with the double-acceptor model, proposed to account for the two impurity levels introduced into Ge by each of the aforementioned impurities.