Bi-induced p-type conductivity in nominally undoped Ga(AsBi)

We report p-type conductivity in nominally undoped GaAs1-xBix epilayers for a wide range of Bi-concentrations (0.6% <= x <= 10.6%). The counterintuitive increase of the conductivity with increasing x is paralleled by an increase in the density of free holes by more than three orders of magnitude in the investigated Bi-concentration range. The p-type conductivity results from holes thermally excited from Bi-induced acceptor levels lying at 26.8 meV above the valence band edge of GaAs1-xBix with concentration up to 2.4 x 10(17) cm(-3) at x = 10.6%. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3690901