Mechanical Behavior of Compound Semiconductors

The semiconductor industry has long been aware of the need to avoid deformation during bulk single-crystal semiconductor growth or during subsequent device processing. The generation of dislocations during liquid-encapsulated Czochralski (LEC) growth of Si, Ge, GaAs, and other III-V compounds is believed to occur when the thermal stress imposed on the crystal during growth exceeds the critical resolved shear stress (CRSS) and the crystal is deformed (Mil'vidskii and Bochkavev, 1978; Jordan et al., 1980, 1984, and 1986). The dislocation density increase that results from deformation has a deleterious effect on the device yield, performance and reliability (Nanishi et al., 1982; Petroff and Hartman, 1973; Miyazawa and Hyuga, 1986). The reduction of thermal stresses during crystal growth and enhancement of crystal strength by doping, such as with In and Si in GaAs (Jordan and Parsey, 1986, 1988; McGuigan et al., 1986) makes possible growth of large single crystals with reduced defects. The deformation behavior of Si and Ge has been a subject of much research for the past three decades while limited studies have been performed on III-V and II-VI compound semiconductors such as GaAs, InP, and CdTe. The mechanical response of these crystals depends on the crystal structure, nature of atomic bonding, concentration of dopants, temperature, and strain or loading rate. In this paper we review the current understanding of the deformation behavior in these materials. Their expected behavior at low, intermediate, and high temperatures, predicted from the current understanding of dislocation motion in solids, is presented along with compressive, tensile, and hardness data on GaAs, InP, CdTe, and Si. The effects of ternary dopants on the mechanical behavior of these materials are analyzed using ideas of solid solution strengthening and defect chemistry. Finally, implications for defect-free crystal growth and device fabrication are examined.