Nucleation and Growth of InAs Islands on GaAs: An Optical Study

Abstract

The observation, as early as 19851–3, of intense photoluminescence (PL) from small InAs clusters in GaAs grown by molecular beam epitaxy (MBE) has opened an outstanding route toward the production of device compatible arrays of semiconductor quantum boxes (QBs) for optoelectronics. The spontaneous formation of dense arrays of small three-dimensional (3D) coherent4,5 islands during the growth of highly strained III–V layers has indeed been used since to produce QBs for various systems (InAs/GaAs1–8, InGaAs/GaAs9–11, InAs/InP12, InGaAs/GaAlAs13, InP/InGaP14…) by either MBE1–10 or chemical vapor deposition techniques11–14 on unpatterned substrates. This fabrication technique of QBs is intrinsically not only much simpler and cheaper than approaches based on the processing of a quantum well (QW)15 or the selective growth on a masked surface16 but also much cleaner. For InAs/GaAs, optical studies have highlighted the resulting excellent optical quality of individual QBs17–19 (long non-radiative lifetime (≈1 ns)17, high radiative quantum yield, narrow PL linewidth (“kT)19, fast carrier capture and relaxation17,19) as well as the large inhomogeneous broadening of the PL emission (”kT) due to the size fluctuations of the QBs. Though laser emission sustained by such a QB active medium has already been reported10, these size fluctuations have to be significantly reduced if one wants such a QB laser to perform better than state of the art QW lasers17. Detailed experimental studies of the nucleation and growth of strained islands is therefore highly desirable in order to understand how this morphological transition occurs, probe how island size fluctuations develop and select appropriate growth conditions.