The scheme of electronic transitions via 0.94, 1.0, 1.2, and 1.3 eV radiative centres in n-GaAs

The dependences of the decay times τ and emission peaks hvm of the 0.94, 1.0, 1.2, and 1.3 eV luminescence bands on the equilibrium electron concentration n0 in n-type GaAs are studied with the aim to arrive at the exact scheme of the electronic transitions leading to the above emission bands. Weak dependences of τ and hvm on n0 for low doping levels (at n0 ⪅ 1017 cm−3) followed by a decrease in τ and an increase in hvm for high doping levels (at n0 ⪆ 1017 cm−3) are observed. From this follows that the emission bands at hvm = 0.94, 1.0, 1.2, and 1.3 eV in n-type GaAs for doping levels below 1017 cm−3 are due to radiative recombination of localized electrons in donor-acceptor pairs and for doping levels above 1017 cm−3 are due to radiative recombination of free electrons with holes at the acceptor levels of the donor-acceptor pairs. The corresponding probabilities are found of electron transitions in the donor-acceptor pairs and the free electron capture coefficients by the pair acceptor levels. Using the scheme established of the electronic transitions a new analysis of temperature dependences of the decay times and emission intensities for the above luminescence bands is made and, as a result, more accurate data for the main recombination parameters of the 0.94, 1.0, 1.2, and 1.3 eV radiative centres are obtained.