The conductivity of $a$-Ge${\mathrm{Se}}_2$ films deposited at 77 K was measured down to 4.2 K at frequencies ranging between 0.1 and 100 kHz. Similarly to $a$-${\mathrm{As}}_2$${\mathrm{Te}}_3$ and $a$-${\mathrm{As}}_2$${\mathrm{Te}}_3$Ge the ac conductivity below 100 K is proportional to ${\omega }^s{T}^n$ with $s=1\mathrm{}$. In contrast with the tellurides, however, the value of $n(\simeq 0.35)$ is essentially the same for as-deposited films and films annealed at 300 K and decreases to $n\simeq 0.1$ when the film is annealed above the glass temperature.

• Received 13 October 1982

DOI:https://doi.org/10.1103/PhysRevB.27.2543