Temperature dependence of the direct band gap of InSb from 80 to 800 K

In this undergraduate student poster, we describe measurements of the dielectric function of bulk InSb near the direct band gap using Fourier-transform infrared (FTIR) spectroscopic ellipsometry from 80 to 800 K in an ultra-high vacuum (UHV) cryostat with diamond windows. Indium antimonide (InSb) is the zinc blende compound semiconductor with the smallest direct band gap ( E₀ = 0.18 eV at room temperature) due to its heavy elements and the large resulting spin-orbit splitting and Darwin shifts. It also has a low melting point of 800 K. Previously, the band gap of InSb has only been measured optically up to room temperature [1] and estimated from Hall effect measurements of the effective mass up to 470 K. Ellipsometry measurements of the direct gap of InSb have been described in [2]. Calculations indicate that InSb should undergo a topological phase transition from semiconductor to semi-metal (and topological insulator) at 600 K. It is interesting to see in the data if this transition occurs below the melting point of InSb.

 

References:

[1] C. L. Littler and D. G. Seiler, Appl. Phys. Lett. 46, 986 (1985).

[2] S. T. Schaefer, S. Gao, P. T. Webster, R. R. Kosireddy, and S. R. Johnson, J. Appl. Phys. 127, 165705 (2020).