Investigation on mechanical characteristics of semi-insulating GaAs crystal under different load

The mechanical properties, such as Vickers microhardness H
_v
, fracture toughness K
_c
, yield strength σ
_v
and brittleness index B
_i
, of a <;100>; oriented semi-insulating GaAs wafer were systematically evaluated using a microindentation technique under 0.025-2 kg applied load. It was found the H
_v
was decreased as the applied load was increased which was mainly attributed to the effect of indenter penetration. The smallest load to introduce indentation on the wafer was calculated to be ~0.004 Kg. However, the K
_c
value was measure nearly a constant (~1.10MPam
^1/2
) under the 0.05-1 Kg load range. The variation of σ
_v
to the applied load was similar to that of H
_v
. The brittleness index B
_i
also exhibited deceasing tendency as the applied load was added. The results implied that the GaAs wafer should be treated carefully during the cutting, polishing and devices fabrication process.