Researchers report simple, nondestructive method to extract minority carrier diffusion lengths

Optimizing the design of optoelectronic devices requires in-depth understanding of material transport properties, such as minority carrier diffusion length and recombination lifetime. Existing methods to measure these parameters have notable disadvantages, such as being time-consuming, complicated, or destructive to the sample.

In Applied Physics Letters, Alexandre Walker and Mike Denhoff from the National Research Council of Canada report a simple, nondestructive, and purely electrical technique to extract minority carrier diffusion lengths, mobilities, and lifetimes. They successfully demonstrate the method using an n-type InP:Si/intrinsic InGaAs/n-type InP:Si double-heterostructure.

The researchers demonstrated placing long, thin diffused junction diodes in a linear geometry, separated by increasing distances. By probing two sets of contacts and measuring the voltage characteristics for various interdiode separations, the experimental data can be fitted to a 1D diffusion equation to reveal heavy and light minority carrier diffusion lengths, and with some assumptions, the mobilities and lifetimes. The method, which is limited to low injection conditions, can also be used to monitor material and fabrication quality across the wafer and from epitaxial run to run.

Walker mentions that many studies rely on accurate measurements of minority carrier diffusion length to gauge material quality. However, the number is often assumed based on other publications because of the time and effort required to actually measure it. With Walker and Denhoff’s method, researchers can easily extract the minority carrier diffusion length, as well as gain insight into mobility and lifetime.

According to Walker, future work will involve applying the method to optimize the design of avalanche photodiodes and focal plane arrays. By publishing the method and preliminary results, he hopes that researchers apply the technique to other materials and report the extracted properties to the scientific community.

Source: “Heavy and light hole minority carrier transport properties in low-doped n-InGaAs lattice matched to InP,” by Alexandre W. Walker and Mike W. Denhoff, Applied Physics Letters (2017). The article can be accessed at https://doi.org/10.1063/1.5002677 .