Polycrystalline GaSb films prepared by the coevaporation technique

Abstract

Gallium antimonide (GaSb) films were deposited onto fused silica and n-Si (100) substrates by coevaporating Ga and Sb from appropriate evaporation sources. The films were polycrystalline in nature. The size and the shape of the grains varied with the change in the substrate temperature during deposition. The average surface roughness of the films was estimated to be 10 nm. Grain boundary trap states varied between 2×10¹² and 2.2×10¹² cm⁻² while barrier height at the grain boundaries varied between 0.09 eV and 0.10 eV for films deposited at higher temperatures. Stress in the films decreased for films deposited at higher temperatures. XPS studies indicated two strong peaks located at ∼543 eV and ∼1121 eV for Sb 3d_3/2 and Ga 2p_3/2 core-level spectra, respectively. The PL spectra measured at 300 K was dominated by a strong peak located ∼0.55 eV followed by two low intensity peaks ∼0.63 eV and 0.67 eV. A typical n-Si/GaSb photovoltaic cell fabricated here indicated V _oc∼311 mV and J∼29.45 mA/cm², the density of donors (N _d)∼3.87×10¹⁵ cm⁻³, built in potential (V _bi)∼0.48 V and carrier life time (τ)∼28.5 ms. Impedance spectroscopy measurements indicated a dielectric relaxation time ∼100 μs.