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

Abstract

Articles you may be interested inInfluence of quantum-confined Stark effect on optical properties within trench defects in InGaN quantum wells with different indium content Quantum-confined stark effect in localized luminescent centers within InGaN/GaN quantum-well based light emitting diodesIn 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 builtin 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. V C 2014 AIP Publishing LLC. [http://dx.

Structural, electronic, and optical properties ofm-plane InGaN/GaN quantum wells: Insights from experiment and atomistic theory

“…First, in polar (In,Ga)N QWs the decay occurs over a much longer time scale due to the polarization field perpendicular to the plane of the QWs [45,[47][48][49]. Second, the decay curves are nonexponential due to the variable in-plane separation of the separately localized electrons and holes [46,49].…”

A comparison of the optical properties of InGaN/GaN multiple quantum well structures grown with and without Si-doped InGaN prelayers

“…The high energy emission was attributed to either carrier recombination in QWs that form on the semi-polar facets of the "V" defects or to the 1st QW in the MQW stack whose properties had been modified by the InGaN prelayer. Subsequently, we have shown 20,21 that the inclusion of a doped GaN or InGaN prelayer beneath a single QW leads to a large blue shift of the PL peak emission energy and a significant reduction in the low temperature (10 K) PL decay time at the PL peak, compared to a single QW structure grown without a prelayer. These observations are compatible with the results of calculations performed using nextnano 3 (nextnano GmbH) which showed a significant reduction in the electric field across the single QW for each structure containing a prelayer due to an enhancement of the surface polarisation field, which opposed the built-in electric field across the QW.…”

“…Typical prelayer structures consist of 20-30 nm of intentionally Si-doped (In)GaN, which can be either a single layer or a short-period superlattice, positioned a few nanometers beneath the 1st QW. The improvements in IQE have been attributed to either increases in the radiative recombination rate 15,16,18,20,21 or decreases in the nonradiative recombination rate. 11,19 Nanhui et al 15,16 reported that the inclusion of an unintentionally doped 20 nm thick In 0.08 Ga 0.92 N layer in an InGaN/GaN multiple QW structure led to an increase in the photoluminescence (PL) intensity at room temperature.…”

Room temperature PL efficiency of InGaN/GaN quantum well structures with prelayers as a function of number of quantum wells

“…External quantum efficiencies as high as 70% [1] occur in c-plane wurtzite (In)GaN despite the large built-in electric field across the QWs due to the discontinuities in the spontaneous polarisation at the interfaces between GaN and InGaN layers, and the piezoelectric polarisation due to the strain in the InGaN layers grown on GaN [2]. There have been several reports [3][4][5][6][7][8][9][10][11][12][13] that the growth of a layer of InGaN, 10s of nm thick and referred to as a prelayer, prior to the first QW in multiple QW (MQW) structures and LEDs leads to increases in the measured luminescence intensity and room temperature (RT) internal quantum efficiency (IQE). Suggestions for the mechanism by which prelayers bring about these improvements have included strain reduction in the QW layers [3], acting as an "electron reservoir" from which carriers tunnel into the QWs [4], and a reduction in the density of point defects in the active region [5,[8][9][10].…”

“…Suggestions for the mechanism by which prelayers bring about these improvements have included strain reduction in the QW layers [3], acting as an "electron reservoir" from which carriers tunnel into the QWs [4], and a reduction in the density of point defects in the active region [5,[8][9][10]. We have previously demonstrated [11][12][13] that the QW IQE improvements associated with the inclusion of prelayers can be explained as being due to the modification of the surface polarisation field between the sample surface and the prelayer which opposes the fields across the QWs. This leads to a reduction in the net electric fields across all of the QWs in the stack.…”