CONDUCTIVITY OF COMPENSATED MODERATELY DOPED p-TYPE Ge AT LOW AND ULTRALOW TEMPERATURES.

The dependences of the conductivity of nuclear-doped p-type Ge on the main impurity concentration N//G//a equals (0. 6-3. 0) multiplied by 10**1**7 cm** minus **3 and on the degree of compensation K equals 0. 1-0. 95 were determined in a wide temperature range (300 equals 0. 06 K). In the range K less than 0. 8 the impurity-band conductivity was governed by two mechanisms: the epsilon //2 conduction associated with the activation of carriers of delocalized states in the impurity band described by sigma equals sigma //0exp( minus DELTA epsilon /kT) and observed at T greater than 1K; the hopping conduction between various states below the delocalization threshold at T less than 1 K characterized first by a constant and then (at lower temperatures) by a variable activation energy sigma varies directly as exp( minus epsilon prime //3/kT) and sigma varies directly as exp left bracket minus (T//0/T)**n right bracket , respectively. It was demonstrated that the epsilon conduction process appeared only together with the epsilon //2 mechanism. The relationships obtained for sigma //0, DELTA epsilon , and epsilon prime //3 were analyzed on the basis of a unified model allowing for changes in the subband of delocalized states in an impurity band due to changes in N//G//a and K.