ENERGY GAP IN HG1-XCDXTE BY OPTICAL ABSORPTION

The absorption coefficient at the fundamental absorption edge has been measured in Hg1-xCdxTe over the composition range 0.23≤x≤0.61 and at temperatures from 300°to 10°K. The energy gap, estimated from the position of the absorption edge, increases continuously with increasing CdTe content but was not linear between the values for HgTe and CdTe. The energy gap of the alloys varied approximately linearly with temperature for T>100°K, going from a positive temperature coefficient for x<0.5 to a negative temperature coefficient for x>0.5. The temperature coefficient of the gap, dEg/dT, was linear with composition and extrapolated to +5.6×10-4 eV/°K for HgTe. The expression Eg(x, T)=-0.303+1.73x+5.6×10-4(1-2x)T+0.25x4 was obtained from the data and can be used to obtain the energy gap as a function of x and T over a large range of these variables. © 1969 The American Institute of Physics.