After the photovoltaic effect was first observed by Reynolds et al.,1 much interest was focused on CdS. CdS is a material which is of importance in phosphors and photoconductors. Since the bandgap of CdS is 2.3 8 eV and of direct transition type, it is a candidate for green light photoelectric conversion devices. CdS is also promising for lasers so that the growth of large single crystals have been attempted.
Typical physical properties are shown in Table 13.1. 2 6 Precise melting point and vapor pressures were determined by Addamiano et al.7 , 8
| Crystal Structure | wurtzite |
|---|---|
| Lattice Constant | a=4.1368 |
| c=6.7163 | |
| Density | 4.82 g/cm 3 |
| Melting Point | 1475 C |
| Linear Expansion Coefficient | 5.0 6.5 10 -6/deg( ?c) |
| 2.5 4.0 10 -6/deg(//c) | |
| Thermal Conductivity | 0.3 W/cm K |
| Dielectric Constant | 10.33 (//), 9.35 ( ?) |
| Refractive index | 2.674 |
| Bandgap at Room Temperature | 2.38 eV |
| Optical Transition Type | direct |
| Intrinsic Carrier Concentration | 16.7 10 15/cm 3(1173K) |
| Electron Mobility at R.T. | 350 cm 2/V sec |
| Hole Mobility at R.T. | 15 cm 2/V sec |
The phase diagram of CdS was reported by Woodbury9 as shown in Fig. 13.1. The lattice parameter of CdS xSe 1-x has been measured by Al-Bassam et al.10
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