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Title: Room temperature negative differential resistance in terahertz quantum cascade laser structures

Abstract

The mechanisms that limit the temperature performance of GaAs/Al{sub 0.15}GaAs-based terahertz quantum cascade lasers (THz-QCLs) have been identified as thermally activated LO-phonon scattering and leakage of charge carriers into the continuum. Consequently, the combination of highly diagonal optical transition and higher barriers should significantly reduce the adverse effects of both mechanisms and lead to improved temperature performance. Here, we study the temperature performance of highly diagonal THz-QCLs with high barriers. Our analysis uncovers an additional leakage channel which is the thermal excitation of carriers into bounded higher energy levels, rather than the escape into the continuum. Based on this understanding, we have designed a structure with an increased intersubband spacing between the upper lasing level and excited states in a highly diagonal THz-QCL, which exhibits negative differential resistance even at room temperature. This result is a strong evidence for the effective suppression of the aforementioned leakage channel.

Authors:
;  [1];  [2]
  1. Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
  2. Center for Integrated Nanotechnologies, Sandia National Laboratories, MS 1303, Albuquerque, New Mexico 87185-1303 (United States)
Publication Date:
OSTI Identifier:
22590517
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 109; Journal Issue: 8; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CHARGE CARRIERS; EXCITATION; EXCITED STATES; GALLIUM ARSENIDES; LANTHANUM SELENIDES; LASERS; LEAKS; PERFORMANCE; PHONONS; SCATTERING; TEMPERATURE RANGE 0273-0400 K

Citation Formats

Albo, Asaf, E-mail: asafalbo@gmail.com, Hu, Qing, and Reno, John L.. Room temperature negative differential resistance in terahertz quantum cascade laser structures. United States: N. p., 2016. Web. doi:10.1063/1.4961617.
Albo, Asaf, E-mail: asafalbo@gmail.com, Hu, Qing, & Reno, John L.. Room temperature negative differential resistance in terahertz quantum cascade laser structures. United States. doi:10.1063/1.4961617.
Albo, Asaf, E-mail: asafalbo@gmail.com, Hu, Qing, and Reno, John L.. 2016. "Room temperature negative differential resistance in terahertz quantum cascade laser structures". United States. doi:10.1063/1.4961617.
@article{osti_22590517,
title = {Room temperature negative differential resistance in terahertz quantum cascade laser structures},
author = {Albo, Asaf, E-mail: asafalbo@gmail.com and Hu, Qing and Reno, John L.},
abstractNote = {The mechanisms that limit the temperature performance of GaAs/Al{sub 0.15}GaAs-based terahertz quantum cascade lasers (THz-QCLs) have been identified as thermally activated LO-phonon scattering and leakage of charge carriers into the continuum. Consequently, the combination of highly diagonal optical transition and higher barriers should significantly reduce the adverse effects of both mechanisms and lead to improved temperature performance. Here, we study the temperature performance of highly diagonal THz-QCLs with high barriers. Our analysis uncovers an additional leakage channel which is the thermal excitation of carriers into bounded higher energy levels, rather than the escape into the continuum. Based on this understanding, we have designed a structure with an increased intersubband spacing between the upper lasing level and excited states in a highly diagonal THz-QCL, which exhibits negative differential resistance even at room temperature. This result is a strong evidence for the effective suppression of the aforementioned leakage channel.},
doi = {10.1063/1.4961617},
journal = {Applied Physics Letters},
number = 8,
volume = 109,
place = {United States},
year = 2016,
month = 8
}
  • The mechanisms that limit the temperature performance of GaAs/Al 0.15GaAs-based terahertz quantum cascade lasers (THz-QCLs) have been identified as thermally activated LO-phonon scattering and leakage of charge carriers into the continuum. Consequently, the combination of highly diagonal optical transition and higher barriers should significantly reduce the adverse effects of both mechanisms and lead to improved temperature performance. Here, we study the temperature performance of highly diagonal THz-QCLs with high barriers. Our analysis uncovers an additional leakage channel which is the thermal excitation of carriers into bounded higher energy levels, rather than the escape into the continuum. Based on this understanding,more » we have designed a structure with an increased intersubband spacing between the upper lasing level and excited states in a highly diagonal THz-QCL, which exhibits negative differential resistance even at room temperature. Furthermore, this result is a strong evidence for the effective suppression of the aforementioned leakage channel.« less
  • We present current density-voltage characteristics of Ge quantum dot p{sup +}-i-n{sup +} tunneling diodes. The diode structure with Ge quantum dots embedded in the intrinsic region was grown by low temperature molecular beam epitaxy without any postgrowth annealing steps. The quantum dot diodes were fabricated using a low thermal budget fabrication process which preserves the Ge quantum structure. A negative differential resistance at room temperature of a Ge quantum dot tunneling diode was observed. A maximum peak to valley ratio of 1.6 at room temperature was achieved.
  • We investigate the performance of terahertz quantum cascade lasers (THz-QCLs) based on Al{sub x}Ga{sub 1−x}As/Al{sub y}Ga{sub 1−y}As and GaSb/AlGaSb material systems to realize higher-temperature operation. Calculations with the non-equilibrium Green's function method reveal that the AlGaAs-well-based THz-QCLs do not show improved performance, mainly because of alloy scattering in the ternary compound semiconductor. The GaSb-based THz-QCLs offer clear advantages over GaAs-based THz-QCLs. Weaker longitudinal optical phonon–electron interaction in GaSb produces higher peaks in the spectral functions of the lasing levels, which enables more electrons to be accumulated in the upper lasing level.
  • AlN/GaN resonant tunneling diodes grown on low dislocation density semi-insulating bulk GaN substrates via plasma-assisted molecular-beam epitaxy are reported. The devices were fabricated using a six mask level, fully isolated process. Stable room temperature negative differential resistance (NDR) was observed across the entire sample. The NDR exhibited no hysteresis, background light sensitivity, or degradation of any kind after more than 1000 continuous up-and-down voltage sweeps. The sample exhibited a ∼90% yield of operational devices which routinely displayed an average peak current density of 2.7 kA/cm{sup 2} and a peak-to-valley current ratio of ≈1.15 across different sizes.
  • Abstract not provided.