Driving up the quality of metal organic chemical vapor deposition-grown epitaxial wafers for highly innovative photonic applications

Abstract

Quantum cascade lasers (QCL) and extended InGaAs photodetectors (ex-PDs) (operating in regime 1.9–2.6 µm wavelength) are very attractive materials for use in sophisticated photonics and microelectronics such as optical recording, scanners, laser spectroscopy, thermal or gas sensing. Once a laboratory curiosity, QCLs and ex-PDs are now becoming commercially available products, shaping exciting applications. In this work, we present the intricacies and challenges of the development and industrial production of Metal Organic Chemical Vapor Deposition (MOCVD)-grown QCL and ex-PD structures as well as demonstrate their viability for large-scale manufacturing.Different types of epitaxial structures were grown using a multi-wafer production MOCVD system, in 12 × 3″ wafer configuration per growth run. Structural and electrical properties of epitaxial layers were carefully examined.MOCVD growing of QCL and ex-PD structures is a very demanding process. MOCVD production reactor enables development of highly complicated chemical reactions, however, as gas residence is much longer than in small R&D systems, the hetero-interfaces of InGaAs/InAlAs are inevitably graded, which negatively impacts optical and electrical parameters of QCL devices. In addition, QCL structure requires the exact layer thickness as well as absolute precision and repeatability when developing strained InAlAs and InGaAs epi‑layers. In the case of ex-PDs fabrication, the crucial thing is to develop a specially designed and graded buffer layer, and to avoid numerous misfit defects and anomalies in dark current. We obtained high crystallographic quality and repeatability of the epi‑layers, which resulted in QCL high-performance continuous-wave operation and fabrication of ex-PDs with low dark current density (less than 1 × 10−4 A/cm2 at -100 mV/room temperature (RT)) achieving results consistent with Rule07 and higher quantum efficiency.