High Bandwidth Planar InP/InGaAs Avalanche Photodiodes.

We have developed a planar InP/InGaAs APD with high bandwidth for use in high bit rate lightwave systems. The material structure is grown by Trichloride VPE and includes an InGaAsP interface layer to reduce trapping. We have measured gain-bandwidth products up to 70 GHz and bandwidths >5 GHz at M=10. The APDs have typical primary dark currents of 5 nA an capacitances 0.2 pF. In this paper we discuss the design, fabrication and performance of the planar APDs. We also show that understanding the equivalent circuit of the APD is required to determine the intrinsic APD bandwidth and that the gain-bandwidth product is a strong function of the heterointerface field.