skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: The effects of Si-doped prelayers on the optical properties of InGaN/GaN single quantum well structures

Abstract

In this paper, we report on the effects of including Si-doped (In)GaN prelayers on the low temperature optical properties of a blue-light emitting InGaN/GaN single quantum well. We observed a large blue shift of the photoluminescence peak emission energy and significant increases in the radiative recombination rate for the quantum well structures that incorporated Si-doped prelayers. Simulations of the variation of the conduction and valence band energies show that a strong modification of the band profile occurs for the quantum wells on Si-doped prelayers due to an increase in strength of the surface polarization field. The enhanced surface polarization field opposes the built-in field across the quantum well and thus reduces this built-in electric field. This reduction of the electric field across the quantum well reduces the Quantum Confined Stark Effect and is responsible for the observed blue shift and the change in the recombination dynamics.

Authors:
;  [1]; ; ; ;  [2]
  1. School of Physics and Astronomy, Photon Science Institute, University of Manchester, Manchester M13 9PL (United Kingdom)
  2. Department of Material Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom)
Publication Date:
OSTI Identifier:
22311020
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 9; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; DOPED MATERIALS; ELECTRIC FIELDS; GALLIUM NITRIDES; INDIUM COMPOUNDS; MODIFICATIONS; OPTICAL PROPERTIES; PHOTOLUMINESCENCE; POLARIZATION; QUANTUM WELLS; RECOMBINATION; SILICON ADDITIONS; SIMULATION; STARK EFFECT; SURFACES; VALENCE; VISIBLE RADIATION

Citation Formats

Davies, M. J., E-mail: Matthew.Davies-2@Manchester.ac.uk, Dawson, P., Massabuau, F. C.-P., Oliver, R. A., Kappers, M. J., and Humphreys, C. J.. The effects of Si-doped prelayers on the optical properties of InGaN/GaN single quantum well structures. United States: N. p., 2014. Web. doi:10.1063/1.4894834.
Davies, M. J., E-mail: Matthew.Davies-2@Manchester.ac.uk, Dawson, P., Massabuau, F. C.-P., Oliver, R. A., Kappers, M. J., & Humphreys, C. J.. The effects of Si-doped prelayers on the optical properties of InGaN/GaN single quantum well structures. United States. doi:10.1063/1.4894834.
Davies, M. J., E-mail: Matthew.Davies-2@Manchester.ac.uk, Dawson, P., Massabuau, F. C.-P., Oliver, R. A., Kappers, M. J., and Humphreys, C. J.. Mon . "The effects of Si-doped prelayers on the optical properties of InGaN/GaN single quantum well structures". United States. doi:10.1063/1.4894834.
@article{osti_22311020,
title = {The effects of Si-doped prelayers on the optical properties of InGaN/GaN single quantum well structures},
author = {Davies, M. J., E-mail: Matthew.Davies-2@Manchester.ac.uk and Dawson, P. and Massabuau, F. C.-P. and Oliver, R. A. and Kappers, M. J. and Humphreys, C. J.},
abstractNote = {In this paper, we report on the effects of including Si-doped (In)GaN prelayers on the low temperature optical properties of a blue-light emitting InGaN/GaN single quantum well. We observed a large blue shift of the photoluminescence peak emission energy and significant increases in the radiative recombination rate for the quantum well structures that incorporated Si-doped prelayers. Simulations of the variation of the conduction and valence band energies show that a strong modification of the band profile occurs for the quantum wells on Si-doped prelayers due to an increase in strength of the surface polarization field. The enhanced surface polarization field opposes the built-in field across the quantum well and thus reduces this built-in electric field. This reduction of the electric field across the quantum well reduces the Quantum Confined Stark Effect and is responsible for the observed blue shift and the change in the recombination dynamics.},
doi = {10.1063/1.4894834},
journal = {Applied Physics Letters},
number = 9,
volume = 105,
place = {United States},
year = {Mon Sep 01 00:00:00 EDT 2014},
month = {Mon Sep 01 00:00:00 EDT 2014}
}
  • In this paper, we report on a detailed spectroscopic study of the optical properties of InGaN/GaN multiple quantum well structures, both with and without a Si-doped InGaN prelayer. In photoluminescence and photoluminescence excitation spectroscopy, a 2nd emission band, occurring at a higher energy, was identified in the spectrum of the multiple quantum well structure containing the InGaN prelayer, originating from the first quantum well in the stack. Band structure calculations revealed that a reduction in the resultant electric field occurred in the quantum well immediately adjacent to the InGaN prelayer, therefore leading to a reduction in the strength of themore » quantum confined Stark effect in this quantum well. The partial suppression of the quantum confined Stark effect in this quantum well led to a modified (higher) emission energy and increased radiative recombination rate. Therefore, we ascribed the origin of the high energy emission band to recombination from the 1st quantum well in the structure. Study of the temperature dependent recombination dynamics of both samples showed that the decay time measured across the spectrum was strongly influenced by the 1st quantum well in the stack (in the sample containing the prelayer) leading to a shorter average room temperature lifetime in this sample. The room temperature internal quantum efficiency of the prelayer containing sample was found to be higher than the reference sample (36% compared to 25%) which was thus attributed to the faster radiative recombination rate of the 1st quantum well providing a recombination pathway that is more competitive with non-radiative recombination processes.« less
  • Data on the temperature dependence of the cathodoluminescence intensity in multiple InGaN/GaN quantum-well structures in the temperature range 80–300 K are reported. Unirradiated structures and structures irradiated with electrons with subthreshold energy are studied. It is shown that, upon irradiation, the temperature dependence becomes weaker. From analysis of the results obtained in this study and previously, it can be suggested that electron irradiation initiates the relaxation of strains produced in quantum wells due to the InGaN-GaN lattice mismatch.
  • Effects of well thickness and Si doping on the optical properties of GaN/AlGaN (MQWs) have been investigated by picosecond time-resolved photoluminescence (PL) measurements. Our results have yielded that (i) the optical transitions in nominally undoped MQWs with narrow well thicknesses (L{sub w}{lt}40{Angstrom}) were blue shifted with respect to the GaN epilayer due to quantum confinement, however, no such blue shift was evident for the MQWs with well thicknesses larger than 40 {Angstrom}, (ii) the band-to-impurity transitions were the dominant emission lines in nominally undoped MQWs of large well thicknesses (L{sub w}{gt}40{Angstrom}) at low temperatures, and (iii) Si doping improved significantlymore » the crystalline quality of MQWs of large well thicknesses (L{sub w}{gt}40{Angstrom}). The implications of these results on the device applications based on III-nitride MQWs have been discussed. {copyright} {ital 1997 American Institute of Physics.}« less
  • Partial strain relaxation effects on polarization anisotropy of semipolar (112{sup ¯}2) InGaN/GaN quantum well (QW) structures were investigated using the multiband effective-mass theory. In the case of strain relaxation of ϵ{sub x′x′} along x′-axis, the polarization ratio gradually decreases with increasing strain relaxation. Also, with the strain relaxation by the same amount, the variation of the polarization ratio along x′-axis is shown to be much larger than that along y′-axis. However, the polarization switching is not observed even at a high In composition of 0.4 due to a small strain component (ϵ{sub x′x′}{sup 0}) with no strain relaxation. On themore » other hand, in the case of strain relaxation of ϵ{sub y′y′} along y′-axis, the polarization switching is observed, and the optical anisotropy is found to change from positive to negative with increasing strain relaxation. Also, the absolute value of the polarization ratio gradually decreases with increasing carrier density. However, the polarization switching due to the carrier density is not observed. Thus, the polarization switching observed at high carrier density may be attributed to inhomogeneous strain distribution in the InGaN layer.« less
  • The spectra of electroluminescence, photoluminescence, and photocurrent for the In{sub 0.2}Ga{sub 0.8}N/GaN quantum-well structures are studied to clarify the causes for the reduction in quantum efficiency with increasing forward current. It is established that the quantum efficiency decreases as the emitting photon energy approaches the mobility edge in the In{sub 0.2}Ga{sub 0.8}N layer. The mobility edge determined from the photocurrent spectra is E{sub me} = 2.89 eV. At the photon energies hv > 2.69 eV, the charge carriers can tunnel to nonradiative recombination centers with a certain probability, and therefore, the quantum efficiency decreases. The tunnel injection into deep localizedmore » states provides the maximum electroluminescence efficiency. This effect is responsible for the origin of the characteristic maximum in the quantum efficiency of the emitting diodes at current densities much lower than the operating densities. Occupation of the deep localized states in the density-of-states 'tails' in InGaN plays a crucial role in the formation of the emission line as well. It is shown that the increase in the quantum efficiency and the 'red' shift of the photoluminescence spectra with the voltage correlate with the changes in the photocurrent and occur due to suppression of the separation of photogenerated carriers in the field of the space charge region and to their thermalization to deep local states.« less