Estimation of sidewall nonradiative recombination in GaInAsP/InP wire structures fabricated by low energy electron-cyclotron-resonance reactive-ion-beam-etching

Surface quality of an etched sidewall of GaInAsP/InP narrow wire structures fabricated by low-energy electron-cyclotron-resonance reactive-ion-beam-etching (ECR-RIBE) using pure Cl-2 gas or Cl-2/H-2 gas mixture was investigated by measuring photoluminescence (PL) intensity dependence on the wire width from 2 mu m to 30-40 nm. Measured PL intensity dependence on the wire width was fairly consistent with that given by a previously reported model, and it was characterized by sidewall recombination velocity and dead-layer thickness. The product of the sidewall recombination velocity and the carrier lifetime S.tau was estimated to be around 200 nm (as-etched) at room temperature (297 K) for air-post wire structures etched from a GaInAsP/InP single-quantum-well wafer with pure Cl-2 gas. It was reduced to 140 nm after a shallow (2 nm) wet etching. These S.tau values are, to our knowledge, among the lowest of those reported on GaInAsP/InP air-post wire structures fabricated by several dry etching schemes. An introduction of Cl-2/H-2 mixture gas was found to effectively reduce it to 140 nm (as-etched) and to 92 nm after shallow wet etching. When this dry etching process was applied to the GaInAs/InP 5-quantum-well wafer, a PL intensity comparable to that by conventional wet etching (S.tau value: 62 nm) was obtained with a. wire width of around 40 nm. These results indicate that our ECR-RIBE method which utilizes negative acceleration bins voltage to the sample is promising for producing a fine-sized stacked multiple layer structure with better size uniformity than the conventional wet etching process.