Abstract
Photoluminescence (PL) studies in GaN thin films grown by infrared close space vapor transport (CSVT-IR) in vacuum are presented in this work. The growth of GaN thin films was done on a variety of substrates like silicon, sapphire and fused silica. Room temperature PL spectra of all the GaN films show near band-edge emission (NBE) and a broad blue and green luminescence (BL, GL), which can be seen with the naked eye in a bright room. The sample grown by infrared CSVT on the silicon substrate shows several emission peaks from 2.4 to 3.22 eV with a pronounced red shift with respect to the band gap energy. The sample grown on sapphire shows strong and broad ultraviolet emission peaks (UVL) centered at 3.19 eV and it exhibits a red shift of NBE. The PL spectrum of GaN films deposited on fused silica exhibited a unique and strong blue-green emission peak centered at 2.38 eV. The presence of yellow and green luminescence in all samples is related to native defects in the structure such as dislocations in GaN and/or the presence of amorphous phases. We analyze the material quality that can be obtained by CSVT-IR in vacuum, which is a high yield technique with simple equipment set-up, in terms of the PL results obtained in each case.
Highlights
Many semiconductor materials have been studied for their potential application in solar cells taking advantage of the possibility to perform band-gap-engineering, as well as the tailoring of optical and electrical material properties towards optimal solar-conversion performance in these devices
Several gallium nitride (GaN)-thin film samples were processed over different substrates by the CSVT-IR technique and characterized by room-temperature photoluminescence
GaN thin films grown by CSVT-IR, do not have a stoichiometric composition and they contain point defects such as nitrogen and gallium vacancies and the inclusion of impurities (C, O) that produce radiative transitions observed in PL experiments
Summary
Many semiconductor materials have been studied for their potential application in solar cells taking advantage of the possibility to perform band-gap-engineering, as well as the tailoring of optical and electrical material properties towards optimal solar-conversion performance in these devices. In this paper we propose a method that can be used to fabricate GaN thin films, namely, the deposition technique by infrared close space vapor transport (CSVT-IR), which has several advantages over MBE and MOCVD, such as a simple equipment set-up and high yield. This technique has been used to grow other materials such as CdTe and CdS at laboratory level and in industrial processes. We show that it is possible to obtain high quality GaN polycrystalline thin films by CSVT-IR for potential applications in solar cell devices
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