Electrical Properties, Deep Levels Spectra and Luminescence of Undoped GaN/InGaN Multi-quantum-well Structures as Affect
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Electrical Properties, Deep Levels Spectra and Luminescence of Undoped GaN/InGaN Multi-quantum-well Structures as Affected by Electron Irradiation Alexander Y Polyakov1, Nikolai B Smirnov1, Anatoliy V Govorkov1, Alexander V Markov1, Cheul-Ro Lee2, In-Hwan Lee2, Nikolai G Kolin3, Denis I Merkurisov3, Vladimir M Boiko3, and James S Wright4 1 Physics, Institute of Rare Metals, B. Tolmachevsky, 5, Moscow, 119270, Russian Federation 2 School of Advanced Materials Engineering and Research Center for Advanced Materials Development, Eng, Chonbuk National University, Chonju 561-756, Chonju, 561-756, Korea, Republic of 3 Obninsk Branch of Federal State Enterprise, Karpov Institute of Physical Chemistry, Kiev Avenue, Obninsk, Kaluga Region, 249033, Russian Federation 4 Materials Science and Engineering, University of Florida, Gainesville, FL, 32611
ABSTRACT Current-voltage, capacitance-voltage characteristics, admittance spectra, deep traps spectra (DLTS), microcathodoluminescence (MCL) spectra of undoped n-GaN/InGaN multiquantum well (MQW) structures were studied before and after 10 MeV electron irradiation. The current flow in the studied structures was found to be determined by strong tunneling while the presence of piezoelectric field manifested itself in the red spectral shift of the quantum well related peak and a marked dependence of the peak position on applied external electric field. DLTS spectra showed unusual features that could be related to transient screening of polarization charges. Electron irradiation introduced a high density of band-like states that could be due to interface traps in the MQWs.
INTRODUCTION GaN and related III-nitrides are rapidly becoming the second most practically important semiconductor materials system after silicon, with multiple applications in visible/UV light emitters/detectors, high-power/high-frequency transistors, etc. Among these materials the properties of GaN/InGaN multiple quantum wells (MQWs) arise much interest because they are an integral part of GaN/InGaN based light emitting diodes. In such MQW structures the role of piezoelectric field has been shown to be of utmost importance [1]. Various tunneling effects have also been shown to play an important role. Despite a large amount of work devoted to this topic not much has been done so far to study the deep levels spectra in GaN/InGaN QWs and the impact of ionizing radiation on these structures. The latter is important because of potential use of GaN/InGaN based light emitting diodes (LEDs) in space systems where they can be subjected to high energy electron and proton bombardment. In what follows we present the preliminary results of such studies for undoped n-GaN/InGaN MQW structures before and after irradiation with 10 MeV electrons.
EXPERIMENTAL, RESULTS, DISCUSSION n-GaN (undoped, 2 µm)/n-GaN(Si doped, 2 µm)/5 QW GaN(14 nm)/InGaN (2.5 nm)/nGaN(undoped, 60 nm) MQW structures were grown by MOCVD on sapphire.Essentially, the studied structures mimicked the structure of the blue LEDs, but for the absence o
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