Micro-PL analysis of high current density resonant tunneling diodes for THz applications

Low-temperature micro-photoluminescence (mu PL) is used to evaluate wafer structural uniformity of current densities >5mA/mu m(2) InGaAs/AlAs/InP resonant tunneling diode (RTD) structures on different length scales. Thin, highly strained quantum wells (QWs) are subject to monolayer fluctuations, leading to a large statistical distribution in their electrical properties. This has an important impact on the RTD device performance and manufacturability. The PL spot size is reduced using a common photolithography mask to reach a typical high J(peak) for a given RTD mesa size (1 similar to 100 mu m(2)). We observe that for lower strain-budget samples, the PL line shape is essentially identical for all excitation/collection areas. For higher strain-budget samples, there is a variation in the PL line shape that is discussed in terms of a variation in long-range disorder brought about by strain relaxation processes. The RTD operating characteristics are discussed in light of these findings, and we conclude that strain model limits overestimate the strain budget that can be incorporated in these devices. We also highlight mu PL as a powerful nondestructive characterization method for RTD structures.

Automated summary

The study uses low-temperature micro-photoluminescence (mu PL) to evaluate wafer structural uniformity of InGaAs/AlAs/InP resonant tunneling diode (RTD) structures, finding that thin quantum wells exhibit fluctuations leading to non-uniform electrical properties. The use of a common photolithography mask reduces the PL spot size, and variations in PL line shape for different strain-budget samples are discussed in terms of long-range disorder brought about by strain relaxation processes. The study concludes that strain model limits may overestimate the strain budget in these devices and highlights mu PL as a powerful nondestructive characterization method for RTD structures.