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Title: Large area InN terahertz emitters based on the lateral photo-Dember effect

Abstract

Large area terahertz emitters based on the lateral photo-Dember effect in InN (indium nitride) are presented. The formation of lateral photo-Dember currents is induced by laser-illumination through a microstructured metal cover processed onto the InN substrate, causing an asymmetry in the lateral photogenerated charge carrier distribution. Our design uses simple metal structures, which are produced by conventional two-dimensional micro-structuring techniques. Having favoring properties as a photo-Dember material InN is particularly well-suited as a substrate for our emitters. We demonstrate that the emission intensity of the emitters can be significantly influenced by the structure of the metal cover leaving room for improvement by optimizing the masking structures.

Authors:
; ;  [1];  [2]; ; ; ;  [3]
  1. Department of Molecular and Optical Physics, University of Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg (Germany)
  2. (Germany)
  3. Fraunhofer-Institut für Angewandte Festkörperphysik, Tullastr. 72, 79108 Freiburg (Germany)
Publication Date:
OSTI Identifier:
22482064
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 107; Journal Issue: 11; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ASYMMETRY; CHARGE CARRIERS; DEMBER EFFECT; INDIUM; INDIUM NITRIDES; LASERS; MASKING; MICROSTRUCTURE; OPTIMIZATION; SUBSTRATES

Citation Formats

Wallauer, Jan, E-mail: jan.wallauer@fmf.uni-freiburg.de, Grumber, Christian, Walther, Markus, Freiburg Materials Research Center, University of Freiburg, Stefan-Meier-Str. 21, 79104 Freiburg, Polyakov, Vladimir, Iannucci, Robert, Cimalla, Volker, and Ambacher, Oliver. Large area InN terahertz emitters based on the lateral photo-Dember effect. United States: N. p., 2015. Web. doi:10.1063/1.4930233.
Wallauer, Jan, E-mail: jan.wallauer@fmf.uni-freiburg.de, Grumber, Christian, Walther, Markus, Freiburg Materials Research Center, University of Freiburg, Stefan-Meier-Str. 21, 79104 Freiburg, Polyakov, Vladimir, Iannucci, Robert, Cimalla, Volker, & Ambacher, Oliver. Large area InN terahertz emitters based on the lateral photo-Dember effect. United States. doi:10.1063/1.4930233.
Wallauer, Jan, E-mail: jan.wallauer@fmf.uni-freiburg.de, Grumber, Christian, Walther, Markus, Freiburg Materials Research Center, University of Freiburg, Stefan-Meier-Str. 21, 79104 Freiburg, Polyakov, Vladimir, Iannucci, Robert, Cimalla, Volker, and Ambacher, Oliver. 2015. "Large area InN terahertz emitters based on the lateral photo-Dember effect". United States. doi:10.1063/1.4930233.
@article{osti_22482064,
title = {Large area InN terahertz emitters based on the lateral photo-Dember effect},
author = {Wallauer, Jan, E-mail: jan.wallauer@fmf.uni-freiburg.de and Grumber, Christian and Walther, Markus and Freiburg Materials Research Center, University of Freiburg, Stefan-Meier-Str. 21, 79104 Freiburg and Polyakov, Vladimir and Iannucci, Robert and Cimalla, Volker and Ambacher, Oliver},
abstractNote = {Large area terahertz emitters based on the lateral photo-Dember effect in InN (indium nitride) are presented. The formation of lateral photo-Dember currents is induced by laser-illumination through a microstructured metal cover processed onto the InN substrate, causing an asymmetry in the lateral photogenerated charge carrier distribution. Our design uses simple metal structures, which are produced by conventional two-dimensional micro-structuring techniques. Having favoring properties as a photo-Dember material InN is particularly well-suited as a substrate for our emitters. We demonstrate that the emission intensity of the emitters can be significantly influenced by the structure of the metal cover leaving room for improvement by optimizing the masking structures.},
doi = {10.1063/1.4930233},
journal = {Applied Physics Letters},
number = 11,
volume = 107,
place = {United States},
year = 2015,
month = 9
}
  • The design and performance of bias-free InN-based THz emitters that exploit lateral photocurrents is studied by means of numerical simulations. We use a drift-diffusion model with adjusted carrier temperatures and mobilities. The applicability of this approach is demonstrated by a comparison with results from Monte-Carlo simulations. We consider a simple but robust lateral emitter concept using metal stripes with two different thicknesses with one of them being thin enough to be transparent for THz radiation. This arrangement can be easily multiplexed and the efficiency of this concept has already been demonstrated by experiment for GaAs substrates. In the present study,more » we consider InN, which is known to be an efficient photo-Dember emitter because of its superior transport properties. Our main focus is on the impact of the emitter design on the emission efficiency assuming different operation principles. Both the lateral photo-Dember (LPD) effect and built-in lateral field effects are considered. The appropriate choice of the metal stripe and window geometry as well as the impact of surface Fermi level pinning are investigated in detail, and design guidelines for efficient large area emitters using multiplexed structures are provided. We find that InN LPD emitters do not suffer from Fermi level pinning at the InN surface. The optimum emission efficiency is found for LPD emitter structures having 200 nm wide illumination windows and mask stripes. Emitter structures in which lateral electric fields are induced by the metal mask contacts can have a considerably higher efficiency than pure LPD emitters. In the best case, the THz emission of such structures is increased by one order of magnitude. Their optimum window size is 1 μm without the necessity of a partially transparent set of mask stripes.« less
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  • We demonstrate here an efficient photoconductive THz source with low electrical power consumption. We have increased the maximum THz radiation power emitted from SI-GaAs based photoconductive emitters (PCEs) by two orders of magnitude. By irradiating the SI-GaAs substrate with Carbon-ions up to 2 μm deep, we have created lot of defects and decreased the lifetime of photo-excited carriers inside the substrate. Depending on the irradiation dose, we find 1 to 2 orders of magnitude decrease in total current flowing in the substrate, resulting in subsequent decrease of heat dissipation in the device. This has resulted in increasing maximum cut-off of themore » applied voltage across PCE electrodes to operate the device without thermal breakdown from ∼35 V to >150 V for the 25 μm electrode gaps. At optimum operating conditions, carbon irradiated (10{sup 14} ions/cm{sup 2}) PCEs give THz pulses with power about 100 times higher in comparison to the usual PCEs on SI-GaAs and electrical to THz power conversion efficiency has improved by a factor of ∼800.« less