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Title: Selective thermal terahertz emission from GaAs and AlGaAs

Abstract

The selective thermally stimulated terahertz (THz) radiation emission from GaAs and AlGaAs alloys are experimentally observed at frequencies of coupled oscillations of free electron plasma and different branches of interface AlGaAs optical phonons. The effect of strong absorption of incident radiation with large oblique angle (26°) by heated GaAs and AlGaAs is revealed. The coherent THz radiation emission with the frequency of 7.6 THz from the heated high conductivity GaAs (n = 4 × 10{sup 18 }cm{sup −3}) layer is observed. The results are highly relevant to application in optoelectronic THz devices.

Authors:
; ; ; ; ;  [1]
  1. Semiconductor Physics Institute, Center for Physical Sciences and Technology, Vilnius 01108 (Lithuania)
Publication Date:
OSTI Identifier:
22311012
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; ABSORPTION; ALLOYS; ALUMINIUM COMPOUNDS; ELECTRONS; EMISSION; EQUIPMENT; GALLIUM ARSENIDES; INTERFACES; LAYERS; OSCILLATIONS; PHONONS; PLASMA; THZ RANGE

Citation Formats

Požela, K., E-mail: kpozela@pfi.lt, Širmulis, E., Kašalynas, I., Šilėnas, A., Požela, J., and Jucienė, V. Selective thermal terahertz emission from GaAs and AlGaAs. United States: N. p., 2014. Web. doi:10.1063/1.4894539.
Požela, K., E-mail: kpozela@pfi.lt, Širmulis, E., Kašalynas, I., Šilėnas, A., Požela, J., & Jucienė, V. Selective thermal terahertz emission from GaAs and AlGaAs. United States. doi:10.1063/1.4894539.
Požela, K., E-mail: kpozela@pfi.lt, Širmulis, E., Kašalynas, I., Šilėnas, A., Požela, J., and Jucienė, V. Mon . "Selective thermal terahertz emission from GaAs and AlGaAs". United States. doi:10.1063/1.4894539.
@article{osti_22311012,
title = {Selective thermal terahertz emission from GaAs and AlGaAs},
author = {Požela, K., E-mail: kpozela@pfi.lt and Širmulis, E. and Kašalynas, I. and Šilėnas, A. and Požela, J. and Jucienė, V.},
abstractNote = {The selective thermally stimulated terahertz (THz) radiation emission from GaAs and AlGaAs alloys are experimentally observed at frequencies of coupled oscillations of free electron plasma and different branches of interface AlGaAs optical phonons. The effect of strong absorption of incident radiation with large oblique angle (26°) by heated GaAs and AlGaAs is revealed. The coherent THz radiation emission with the frequency of 7.6 THz from the heated high conductivity GaAs (n = 4 × 10{sup 18 }cm{sup −3}) layer is observed. The results are highly relevant to application in optoelectronic THz devices.},
doi = {10.1063/1.4894539},
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}
}
  • Terahertz emission spectra in a longitudinal electric field and lateral photoconductivity spectra under terahertz illumination have been studied in structures with GaAs/AlGaAs quantum wells (QWs). It is shown that the spectra contain features associated with electron transitions involving resonant impurity states related to the second quantum-well subband. Calculations of the energy spectrum of impurity states and matrix elements of optical transitions made by taking into account various positions of the impurity relative to the QW center confirm the assumptions made.
  • We report the observation and the study of an additional shift current tensor element in (110)-oriented GaAs quantum wells, which arises from an out-of-plane asymmetry of the quantum well structure. The current resulting from this tensor element is optically induced with 150 fs laser pulses and detected by measuring the simultaneously emitted terahertz radiation. This terahertz spectroscopy of shift currents is a powerful technique for symmetry investigations, which shows, for example, that our nominally symmetric (110)-oriented GaAs/AlGaAs quantum wells grown by molecular beam epitaxy are in reality asymmetric structures with different right and left interfaces.
  • We report on the intense terahertz emission from InAs/GaAs quantum dot (QD) structures grown by molecular beam epitaxy. Results reveal that the QD sample emission was as high as 70% of that of a p-type InAs wafer, the most intense semiconductor emitter to date. Excitation wavelength studies showed that the emission was due to absorption in strained undoped GaAs, and corresponds to a two order-of-magnitude enhancement. Moreover, it was found that multilayer QDs emit more strongly compared with a single layer QD sample. At present, we ascribe the intense radiation to huge strain fields at the InAs/GaAs interface.
  • The relationship between spontaneous and stimulated emission from a variety of AlGaAs-GaAs double-heterostructure laser diodes has been studied as a function of temperature over a range of 10--70 /sup 0/C. The spontaneous emission varied exponentially with temperature, and we introduce T/sup prime//sub 0/(J) as the characteristic temperature of spontaneous emission. As the temperature was changed, the laser threshold and slope efficiency for a device strongly covaried with spontaneous emission. A moderately high correlation (r>0.75) was obtained between the lasing and spontaneous emission slope efficiencies of 20 randomly selected lasers from different suppliers.
  • Second-harmonic (SH) emission in the form of Cerenkov-type phase-matched radiation has been measured for quantum-cascade lasers (QCLs) with built-in nonlinearities. The QCLs operate at 10.9 {mu}m wavelength and, due to material dispersion, show a high collinear phase mismatch, resulting in low SH external conversion efficiencies on the order of 2 {mu}W/W{sup 2}. Due to our waveguide design, we were able to couple out and measure the generated SH light in the form of Cerenkov-type phase-matched radiation from the substrate of the device. The SH power collected from the Cerenkov beam leads to an increased external conversion efficiency of {approx}50 {mu}W/W{supmore » 2}.« less