High-temperature hardness of bulk single-crystal gallium nitride - in comparison with other wide-gap materials

The hardness of single-crystal gallium nitride of 500 µm thickness at elevated temperatures is measured and compared with those of other semiconductors. A Vickers indentation method was used to determine the hardness under an applied load of 0.5-5 N in the temperature range 20-1200 °C. The average hardness is 10.8 GPa at room temperature, which is comparable to that of Si. At elevated temperatures, GaN shows higher hardness than Si, GaAs, and ZnSe. A high mechanical stability for GaN at high temperature is deduced.