Confirmation of Existence of Phase Transitions in InSe by Specific Heat Measurement and X-Ray Analysis

Abstract

noted that their results differ from a wurtzite structure only by a discrepancy of 1 ~ ' in the angle 8, hence one might describe their structure as slightly distorted wurtzite. This distortion might be caused by the in-corporation of residual oxygen impurity, since the re-actants were oxides. The structure and lattice pa-rameters are almost identical to the isoelectronic I I I-V compound, GaN (wurtzite structure with a----3.189A and c = 5.185A). The resistivity and Hall coefficient of the ZnGeN2 films were measured using a six contact method. Pure ZnGeN2 was always n-type with electron concentra-tions of 1018-1019 cm-3 and resistivities between 0.3 and 0.4 ohm-cm at room temperature. As might be ex-pected for polycrystall ine samples, room temperature mobilities were low, ranging from 0.5 to 5 cm2/V-sec. Hall constants and resistivities measured vs. tempera-ture were found to be constant throughout he tem-perature range from 100 ~ to 300 ~ Optical absorption measurements of polished ZnGeN2 samples, displayed in Fig. 2, indicate a bandgap of approximately 2.67 eV. In this particular sample, the absorption coeffi-cient at 3.2 eV is approximately 58,000 cm-1. The simi-larity between ZnGeN2 and the analogous I I I-V com-pound GaN is noteworthy, particularly the crystal structure and the high carrier density. Manuscript submitted May 6, 1974; revised manu-script received July 26, 1974. Any discussion of this paper will appear in a Discus-sion Section to be published in the June 1975 JOURNAL. All discussions for the June 1975 Discussion Section should be submitted by Feb. 1, 1975. The publication costs of this article have been as-sisted by Stanford University.