Thermal Study for High-Photocurrent Photodetector in Non-Saturation Region Using Thin Substrate, Thin Absorber, and Flip- Chip Bonding Process

Abstract

We reported a thermal investigation on a photodetector (PD) with a sandwiched structure comprising p-type, intrinsic, and n-type (PIN-PD) layers based on Williams' thermal model. Simulations and measurements of the photocurrent in the linear region, 3-dB bandwidth and thermal analyses were conducted. We found a good agreement between the measured photocurrent and simulations. The measured linear photocurrent of PIN-PD with 50 μm substrate and 0.4 μm absorber was 28 mA at -2 V, which was related to the expected RF output power of +13 dBm at 50 GHz. In addition, thermal analyses evaluated the junction temperature corresponding to the specific measured photocurrent, as well as the 431 K for junction breakdown temperature of the fabricated PD samples. This evaluation further predicted that this type of PIN-PD would reach the thermal breakdown point when the photocurrent was 34 mA at -2 V. Furthermore, with the application of AlN flip-chip bonding, the linear and expected maximum photocurrent were improved to 30 mA and 45 mA, respectively. Finally, we predicted the PD temperature and maximum photocurrent of 55 mA using AlN instead of InP as the main substrate.INDEX TERMS breakdown prediction, high linear photocurrent, PIN-PD, thermal analyses