Abstract
We report on the Mg-doped, indium-rich GaxIn1−xN (x < 30). In the undoped material, the intrinsic electron density is very high and as a result there is no detectable photoconductivity (PC) signal within the range of temperatures of 30 <T < 300 K. In the Mg-doped material however, where the conductivity is reduced, there is a strong PC spectrum with two prominent low-energy peaks at 0.65 and 1.0 eV and one broad high-energy peak at around 1.35 eV. The temperature dependence of the spectral photoconductivity under constant illumination intensity, at T > 150 K, is determined by the longitudinal-optical phonon scattering together with the thermal regeneration of non-equilibrium minority carriers from traps with an average depth of 103 ± 15 meV. This value is close to the Mg binding energy in GaInN. The complementary measurements of transient photoluminescence at liquid He temperatures give the e-A0 binding energy of approximately 100 meV. Furthermore, Hall measurements in the Mg-doped material also indicate an activated behaviour with an acceptor binding energy of 108 ± 20 meV.
Highlights
During the last decade, there has been intense research activity in indium-rich GaInN
Until a few years ago, the commonly accepted value for the InN band gap energy was 1.89 eV [4], but the majority of the results were obtained on samples grown by sputtering technique and were characterised as having a polycrystalline structure
We have studied the Hall effect in undoped and Mg doped samples in darkness and investigated the spectral photoconductivity and photoluminescence in indiumrich GaInN grown by molecular beam epitaxy (MBE)
Summary
There has been intense research activity in indium-rich GaInN. Until a few years ago, the commonly accepted value for the InN band gap energy was 1.89 eV [4], but the majority of the results were obtained on samples grown by sputtering technique and were characterised as having a polycrystalline structure. Most of the theoretical work reported at the time was based on this wrong value for the band gap. In 2001 Inushima et al reported a much lower value of EG = 1.1 eV for the molecular beam epitaxy (MBE)-grown samples [5]. Davydov et al [6] performed optical absorption and photoluminescence measurements and reported band gap energy of 0.9 eV. Since a large number of papers from different research groups have been published reporting a value between 0.65 and 0.9 eV in the MBE-grown material. Davydov et al [8] reported a more orthodox dependence, with a reduction of 23 meV in energy when the temperature is increased from 77 to 300 K
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