Spectral dependence of THz emission from InN and InGaN layers

Ričardas Norkus; Ramūnas Aleksiejūnas; Arūnas Kadys; Marek Kolenda; Gintautas Tamulaitis; Arūnas Krotkus

doi:10.1038/s41598-019-43642-4

Spectral dependence of THz emission from InN and InGaN layers

Sci Rep. 2019 May 8;9(1):7077. doi: 10.1038/s41598-019-43642-4.

Authors

Ričardas Norkus¹, Ramūnas Aleksiejūnas², Arūnas Kadys³, Marek Kolenda³, Gintautas Tamulaitis³, Arūnas Krotkus¹

Affiliations

¹ Center for Physical Sciences and Technology, Saulėtekis av. 3, LT-10257, Vilnius, Lithuania.
² Institute of Photonics and Nanotechnology, Vilnius University, Saulėtekis av. 3, LT-10257, Vilnius, Lithuania. ramunas.aleksiejunas@ff.vu.lt.
³ Institute of Photonics and Nanotechnology, Vilnius University, Saulėtekis av. 3, LT-10257, Vilnius, Lithuania.

Abstract

Spectral dependence of terahertz emission is a sensitive tool to analyze the structure of conduction band of semiconductors. In this work, we investigate the excitation spectra of THz pulses emitted from MOCVD-grown InN and InGaN epitaxial layers with indium content of 16%, 68%, and 80%. In InN and indium-rich InGaN layers we observe a gradual saturation of THz emission efficiency with increasing photon energy. This is in stark contrast to other III-V semiconductors where an abrupt drop of THz efficiency occurs at certain photon energy due to inter-valley electron scattering. From these results, we set a lower limit of the intervalley energy separation in the conduction band of InN as 2.4 eV. In terms of THz emission efficiency, the largest optical-to-THz energy conversion rate was obtained in 75 nm thick In_0.16Ga_0.84N layer, while lower THz emission efficiency was observed from InN and indium-rich InGaN layers due to the screening of built-in field by a high-density electron gas in these materials.

Abstract

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