Hopping photoconductivity and the effectiveness of phonon detection in GaAs:Zn bolometers

We have studied the effect of white light on hopping conduction and the effectiveness of non-equilibrium phonon detection in Zn-doped GaAs bolometers over the temperature range 1.35 K ⩽ T ⩽ 2.15 K. The temperature dependence of the low electric field resistance indicates that the mechanism of conduction is due to variable range hopping. Using a heat-pulse technique we show that the sensitivity of a GaAs:Zn bolometer with an acceptor concentration, na = 4.2 × 1017 cm−3 is significantly enhanced in the presence of suitably applied irradiation, despite the value of its temperature coefficient of resistance, α(T)=(1/R)(∂R/∂T)α(T)=(1/R)(∂R/∂T), actually being decreased by light. It is proposed that the effect of light is to populate excited states of the acceptors, which have larger wave functions and hence show enhanced hopping.