Amorphous InSb and InAs[subscript 0.3]Sb[subscript 0.7] for long wavelength infrared detection

Abstract

The structural, electronic, and optical properties of amorphous InSb and InAs[subscript 0.3]Sb[subscript 0.7] films deposited on Corning glass, Al[subscript 2]O[subscript 3] CdZnTe, SiO[subscript 2]-Si, and CaF2 substrates by Radio Frequency (RF) magnetron sputtering have been studied as they relate to Mid and Long Wavelength Infrared (MWIR and LWIR) detection. Depositions at elevated substrate temperature and pressure of <10mTorr Ar show an emergence of crystalline grains with strong X-ray diffraction peaks at the (111) and (220) orientations. Electronically the amorphous InSb and InAs[subscript 0.3]Sb[subscript 0.7] films deposited at 300K show hopping conduction with resistance in InSb ranging from 44 to 1.1E8 Ω-cm at 300K and 84K respectively. Optical analysis using Fourier transform infrared spectroscopy (FTIR) show the absorption of these films has an absorption tail, the equation of which differing activation energies in InSb and InAs0.3Sb0.7. Amorphous InSb and InAs[subscript 0.3]Sb[subscript 0.7] films showed thermal responsivity in excess of 100V/W for 6μm thick films held at 233K. The maxima and minima of the responsivity are shown to correspond to the interference fringes in the film. The response is highly substrate dependent and compares favorably to other thermal detectors.