2, Sandia National Laboratories, Albuquerque, New Mexico, United States
Epitaxial regrowth essentially involves a multi-sequential material growth process along with intervening wafer processing steps. This process has played a significant role in realizing several semiconductor devices including distributed feedback (DFB) lasers, photonic crystal surface-emitting lasers (PCSELs), transistors and sensors[1-4]. One of the critical factors in this process is the quality of the regrowth interface. The prevention of impurities and abnormalities at this interface is paramount to device performance. In order to obtain good material quality, several parameters such as pre-growth treatments, passivation techniques, surface oxide removal and growth parameters such as growth temperature need to be optimized. This work focuses on developing an epitaxial regrowth process specifically for devices based on quantum-size-controlled photoelectrochemical (QSC-PEC) etching of semiconductor nanostructures. The optimization of the regrowth step is especially significant in QSC-PEC due to the proximity of the active region (quantum wells or quantum dots) to the regrowth interface.
In this work, we have investigated the effect of the regrowth interface on structural and optical properties of pre-grown active components such as InGaAs quantum wells (QWs) or InAs quantum dots (QDs). The structures used in this study are grown using elemental molecular beam epitaxy (MBE) in a VG Semicon V80 reactor on GaAs substrates. The original structures (before regrowth) include InGaAs QWs or InAs QDs grown with different GaAs cap thicknesses, thus varying their proximity to the regrowth interface between 0 and few hundreds of nm. The samples are then exposed to atmosphere before regrowth is attempted. The regrowth process includes pre-treatment for cleaning, surface oxide desorption and an extended GaAs cap at the interface. Different recipes for surface cleaning and both in-situ and ex-situ oxide desorption methods are attempted. A comprehensive photoluminescence (PL) study is carried out from 10K to room temperature to study the effect of the cap thickness and the various cleaning techniques on the optical properties of the QWs and QDs. On the other hand, the effect of these parameters on the structural parameters is studied using X-ray Diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy (TEM). Although the results obtained here are not directly from PEC-etched nanostructures, these findings can be used to tailor the properties of etched nanostructures. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
 Groom, Kristian M. et. al (2009)
 Ha, Yuk L, et al. (2011)
 Hjort, Klas, et al. (1992)
 Noda, Susumu et al. (2017)
 Fischer, Arthur J. et al. (2016)