A Reexamination of Deep Diffused Silicon Avalanche Photodiode Gain and Quantum Efficiency

Abstract

Traditionally the measured gain of an avalanche photodiode (APD) has been considered the product of two parameters. The electron multiplication process being one and the quantum efficiency (QE) the other. The multiplication process is often considered wavelength dependent and the QE being bias independent. We propose a new examination of these related parameters where the APD gain is considered intrinsic, defined as being the amount of electron multiplication each photoelectron undergoes based only on the applied bias and is thus independent of the incident photon wavelength, and where the QE, which can be defined as the number of generated photoelectrons per number of incident photons, is considered intrinsic being a function of not only wavelength, but also bias. This is a more logical, and physically real, perspective of APD behavior. We introduce a technique to measure the intrinsic gain and the intrinsic QE of deep diffused silicon APDs. Once the intrinsic gain vs. bias of the APD is measured, it becomes possible to use this measurement as an absolute parameter. With the intrinsic gain known, we show how the intrinsic QE of an APD, for a given wavelength, changes as a function of bias. We show that when the APD is operated from the low to high gain regime, light at 400 nm to 800 nm experiences an increase in QE. These fundamental, dynamic and operational properties of APDs are critical when considering the wavelength(s) that are of interest for a given application