Optical and Electrical Properties of Vanadium‐Doped GaAs

The results of optical absorption, luminescence, and temperature‐dependent Hall‐effect measurements on GaAs: V, p‐type GaAs: V: Zn, and n‐type GaAs: V:Si grown by LEC‐technique are reported. It is found that the V ground state is located very close to or within the valence band and that the V acceptor level is at Ec − 0.14 eV. The near mid‐gap level in GaAs: V responsible for its semi‐insulating behaviour is proposed to be due to the complex (V ‐ X), where the correlation between the photoionization absorption connected with this centre and the EL2 concentration suggests that X is an arsenic vacancy. From this level scheme conditions for growing GaAs: V which is semi‐insulating at room temperature are derived. The optical experiments on GaAs: V with different Fermi‐level positions confirm the assignment of the triple‐peaked absorption band at 1.1 eV to the 3A2 → 3T1(F) transition of V . The weak absorption due to the 3A2 → 3T2(F) transition is found at 0.79 eV. The analysis of the temperature dependence of the line shape of the → 3T1(F) absorption band as due to strong dynamical T ⊗ τ2 Jahn‐Teller effect provides the JT‐parameters EJT = 780 cm−1, hωτ = 75 cm−1, and c = 4.7 eV/nm. The temperature dependent asymmetry of the line shape is explained on the basis of earlier theoretical predictions of the simultaneous action of strong linear and quadratic JT‐coupling.