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Title: Analysis of the quantum-confined stark effect in InGaN single quantum wells.

Abstract

No abstract prepared.

Authors:
; ;
Publication Date:
Research Org.:
Sandia National Laboratories
Sponsoring Org.:
USDOE
OSTI Identifier:
973652
Report Number(s):
SAND2005-3097J
TRN: US201006%%1046
DOE Contract Number:
AC04-94AL85000
Resource Type:
Journal Article
Resource Relation:
Journal Name: Proposed for publication in Applied Physics Letters.
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; QUANTUM WELLS; STARK EFFECT; PHYSICS

Citation Formats

Koleske, Daniel David, Kaplar, Robert James, and Kurtz, Steven Ross. Analysis of the quantum-confined stark effect in InGaN single quantum wells.. United States: N. p., 2005. Web.
Koleske, Daniel David, Kaplar, Robert James, & Kurtz, Steven Ross. Analysis of the quantum-confined stark effect in InGaN single quantum wells.. United States.
Koleske, Daniel David, Kaplar, Robert James, and Kurtz, Steven Ross. Sun . "Analysis of the quantum-confined stark effect in InGaN single quantum wells.". United States. doi:.
@article{osti_973652,
title = {Analysis of the quantum-confined stark effect in InGaN single quantum wells.},
author = {Koleske, Daniel David and Kaplar, Robert James and Kurtz, Steven Ross},
abstractNote = {No abstract prepared.},
doi = {},
journal = {Proposed for publication in Applied Physics Letters.},
number = ,
volume = ,
place = {United States},
year = {Sun May 01 00:00:00 EDT 2005},
month = {Sun May 01 00:00:00 EDT 2005}
}
  • Here, we report on the optical and structural characteristics of violet-light-emitting, ultra-thin, high-Indium-content (UTHI) InGaN/GaN multiple quantum wells (MQWs), and of conventional low-In-content MQWs, which both emit at similar emission energies though having different well thicknesses and In compositions. The spatial inhomogeneity of In content, and the potential fluctuation in high-efficiency UTHI MQWs were compared to those in the conventional low-In-content MQWs. We conclude that the UTHI InGaN MQWs are a promising structure for achieving better quantum efficiency in the visible and near-ultraviolet spectral range, owing to their strong carrier localization and reduced quantum-confined Stark effect.
  • The trench defects in InGaN/GaN multiple quantum well structures are studied using confocal photoluminescence (PL) spectroscopy and atomic force microscopy. A strong blueshift (up to ∼280 meV) and an intensity increase (by up to a factor of 700) of the emission are demonstrated for regions enclosed by trench loops. The influence of the difference in the well width inside and outside the trench loops observed by transmission electron microscopy, the compositional pulling effect, the strain relaxation inside the loop, and corresponding reduction in the built-in field on the PL band peak position and intensity were estimated. The competition of these effectsmore » is mainly governed by the width of the quantum wells in the structure. It is shown that the PL band blueshift observed within the trench defect loops in the InGaN structures with wide quantum wells is mainly caused by the reduction in efficiency of the quantum-confined Stark effect due to strain relaxation.« less
  • To observe the effects of polarization fields and screening, we have performed contacted electroreflectance (CER) measurements on In{sub 0.07}Ga{sub 0.93}N/GaN single quantum well light emitting diodes for different reverse bias voltages. Room-temperature CER spectra exhibited three features which are at lower energy than the GaN band gap and are associated with the quantum well. The position of the lowest-energy experimental peak, attributed to the ground-state quantum well transition, exhibited a limited Stark shift except at large reverse bias when a redshift in the peak energy was observed. Realistic band models of the quantum well samples were constructed using self-consistent Schroedinger-Poissonmore » solutions, taking polarization and screening effects in the quantum well fully into account. The model predicts an initial blueshift in transition energy as reverse bias voltage is increased, due to the cancellation of the polarization electric field by the depletion region field and the associated shift due to the quantum-confined Stark effect. A redshift is predicted to occur as the applied field is further increased past the flatband voltage. While the data and the model are in reasonable agreement for voltages past the flatband voltage, they disagree for smaller values of reverse bias, when charge is stored in the quantum well, and no blueshift is observed experimentally. To eliminate the blueshift and screen the electric field, we speculate that electrons in the quantum well are trapped in localized states.« less
  • We report comparative studies of 6-nm-thick Al{sub x}Ga{sub 1−x}N/Al{sub y}Ga{sub 1−y}N pyroelectric quantum wells (QWs) grown by plasma-assisted molecular beam epitaxy on c-sapphire substrates with a thick AlN buffer deposited under different growth conditions. The Al-rich growth conditions result in a 2D growth mode and formation of a planar QW, whereas the N-rich conditions lead to a 3D growth mode and formation of a QW corrugated on the size scale of 200–300 nm. Time-resolved photoluminescence (PL) measurements reveal a strong quantum-confined Stark effect in the planar QW, manifested by a long PL lifetime and a red shift of the PLmore » line. In the corrugated QW, the emission line emerges 200 meV higher in energy, the low-temperature PL lifetime is 40 times shorter, and the PL intensity is stronger (∼4 times at 4.5 K and ∼60 times at 300 K). The improved emission properties are explained by suppression of the quantum-confined Stark effect due to the reduction of the built-in electric field within the QW planes, which are not normal to the [0001] direction, enhanced carrier localization, and improved efficiency of light extraction.« less
  • The main characteristics of the quantum confined Stark effect (QCSE) are studied theoretically in quantum wells of Gaussian profile. The semi-empirical tight-binding model and the Green function formalism are applied in the numerical calculations. A comparison of the QCSE in quantum wells with different kinds of confining potential is presented.