Optical Properties of In_(1-x)Ga_xAs_yP_(1-y) Multiple Quantum Well Heterostructural Lasers

摘要

Understanding the physics of In_(1-x)Ga_xAs_yP_(1-y), multiple quantum well (MQW) nanostructures is essential for the development of new photonic devices such as lasers, amplifiers and modulators. In this work, optical and structural properties as well as vertical transport of three different heterostructures grown by metalorganic vapor phase epitaxy and emitting at 1.33 mum and 1.55 have bene studied using continuous wave and time-resolved photoluminescence (cw-PL and TRPL) and high resolution x-ray diffraction (HRXRD). Cw-PL measurements show an anomalous PL characteristics for the structure with a thicker active layer which is discussed in terms of electron-acceptor transitions, donor-acceptor pairs, and constraint relaxation and related structural defects. The overall observed red shift with increasing temperature is interpreted as resulting from two opposite and competitive processes: band-gap shrinkage (dominant) and blue shift caused by fluctuations in the QW layer thickness across the lateral sample direction. In the observed full width at half maximum, we identified a component of approx 8 meV as a contribuftion from longitudinal optical phonons. At high excitation densities, it is shown that carrier spillover and Auger recombination may be the major mechanisms limiting the quantum efficiency. For TRPL measurements, carrier cooling rates are discussed in terms of concurrent and opposite scattering mechanisms. It is found that the rise times of the QWs and the confinement region increase slightly (approx 2 ps) on decreasing the excitation wavelength. The observed difference is attributed to a higher initial carrier temperature associated with the shorter excitation wavelength. Comparable times of approx 4 ps are observed for the carrier transport and relaxation time within the confinement region and the carrier capture time in the quantum wells.