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From measurements of the temperature dependence of the electron concentration in Cd, As"we found values for the conduction-band parameters that are in good agreement with those recently reported by Aubin, Caron, and Jay-Gerin. However, in contrast with these authors we found no small overlap, but a relatively large gap of 26 meV between the heavy-hole band maximum and the conduction-band minimum.In two recent papers' 2 Aubin, Caron, and JayGerin proposed an electronic-energy-band structure of Cd,As, . By gathering the literature values of electron effective masses from electrical transport studies and interpreting these data in Kane's model for the n-Sn type inverted structure, these authors deduced the dispersion relation for the conduction band. The available data on the optical gap were used to determine the position and shape of the heavy-hole band, resulting in band schemes at 300 and 77 K as shown in Fig. 4 of Ref. 1 and Fig. 4 of Ref. 2, respectively. The ever present high degeneracy of this material (a characteristic electron concentration of about 2 x 10" cm ' corresponding to a Fermi energy of about0. 15e&) excluded up to now the determination of both conduction-and valence-band parameters from transport measurements only.We prepared Cd,As2 samples with net donor concentrations almost an order of magnitude lower than those reported in the literature s Samples with initial concentrations of about 2 x 10" cm ' were subjected to various heat treatments in either cadmium or ar senic atmospheres. Reduction of net donor concentrati. ons was found to be most effective by applying a two-stage annealing proce:-dure in arsenic vapor. The samples were first annealed during 1 week at 250'C, followed by a much longer annealing time (2-4 months) at 100 'C. Substantial decrease in net donor concentration with time only started during the second stage of the treatment. A time of over 2 months is needed before a minimum value is achieved.Once the samples are stabilized in this way, their electron concentrations remain constant with time when maintained in air at room temperature.In these samples the degeneracy is partly lifted, and measurements of the electron concentration. n as function of.temperature can be used to obtain numerical values for some important band parameters of the above mentioned model. The n-T dependences of four samples in the temperature range from 4.2 to 360 K are given in Fig.

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