1.3 μM Gasb Metal-Semiconductor-Metal Photodetectors

Abstract

Metal-semiconductor-metal photodetectors employing GaSb active regions and Al<inf>0.5</inf>Ga<inf>0.5</inf>Sb barrier-enhancing abrupt regions have been fabricated on InP substrates to assess the role of hole velocity and to compare with similar photodetectors made using Ga<inf>0.47</inf>In<inf>0.53</inf>As active region. Devices exhibit photoresponse in the 0.2−0.65 A/W range, dark currents of ≈ 10⁻⁶ A at 300 K and ≈ 10⁻¹⁰ A at 77 K for 25 × 25 μm² area, and have a voltage-sensitive 3-dB bandwidth exceeding ≈ 1 GHz at 300 K and 10 GHz at 77 K. The enhanced barrier heights are estimated to be ≈ 0.30 eV. The fall time continues to be the significant component of time delay; its temperature dependence indicates that the hole velocities do improve significantly at lower temperatures. The 300 K behavior appears to be dominated by defect and impurity densities, and the effects of abrupt barriers. The larger than expected dark currents are believed to result from defects associated with lattice mismatch. © 1992 IEEE