Photoconductance measurements on thin InGaN layers

We report photoluminescence (PL), transmission and photoconductance (PC) studies of InxGa1−xN and GaN alloys grown by metalorganic chemical vapor deposition. We demonstrate that PC measurements can provide reliable gap estimates for a large range of film thicknesses in contrast to transmission or ph...

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Veröffentlicht in:Journal of applied physics 2000-11, Vol.88 (9), p.5138-5141
Hauptverfasser: Reverchon, Jean-Luc, Huet, Frédéric, Poisson, Marie-Antoinette, Duboz, Jean-Yves
Format: Artikel
Sprache:eng
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Zusammenfassung:We report photoluminescence (PL), transmission and photoconductance (PC) studies of InxGa1−xN and GaN alloys grown by metalorganic chemical vapor deposition. We demonstrate that PC measurements can provide reliable gap estimates for a large range of film thicknesses in contrast to transmission or photoreflectance experiments. We show that PC measurements give the expected classical value for thick GaN layers by using an elementary model for absorption. They also give the same value as transmission experiments in the case of thin InGaN layers. We have performed PL and PC measurements in InGaN layers. The comparison between the PL peak and PC measurements gives a direct access to the Stokes shift. We study the Stokes shift as a function of temperature. Depending on the particular film, the Stokes shift can be explained in terms of localization or the Burstein–Moss effect. Indeed, Hall measurements show a high electron concentration in some of the films. Thus, our measurements show that very homogeneous InGaN layers with high indium content (22%) can be obtained with a very small Stokes shift and with a very narrow PL peak. In addition, we give the temperature dependence of the InGaN band-gap.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.1289222