Carrier lifetimes in n-type gold-doped germanium

Abstract

Minority and majority carrier lifetimes in n-type gold-doped germanium have been evaluated by means of the combined photoconductive and photoelectromagnetic effects. The room temperature capture cross-section of the upper gold level for electrons is evaluated to be 1.0 (± 0.3) × 10 −16 cm 2 and for holes 1.5 ( ± 1.0) × 10 −12 cm 2. These values agree with the order of magnitude values found by J ohnson and L evinstein( 3). Between 150° and 60°K an exponential temperature dependence is found for the electron capture cross-section with an activation energy of 0.01 eV. Between room temperature and 400°K, surface recombination effects are important, but the PC/PEM ratio method permits the evaluation of the now nearly equal electron and hole lifetimes. Equations are derived for the electron carrier concentration temperature dependence, with partial compensation of the gold level 0.20 eV from the conduction band. The expression is used to evaluate the donor and acceptor concentrations: N d = 4.7 × 10 15/ cm 3 and N a = 2.9 × 10 15/ cm 3. In analysing the data, a mobility ratio of 1·2 at 370°K is required to make the observed data agree with the calculations.