Power Loss Mechanisms in Indium-Rich InGaN Samples ENGIN TIRAS, 1,4 SELMAN MUTLU, 2 and NACI BALKAN 3 1.—Department of Physics, Faculty of Science, Anadolu University, 26470 Yunus Emre Campus, Eskisehir, Turkey. 2.—Department of Physics, Faculty of Science, _ Istanbul University, 34134 Vezneciler, Istanbul, Turkey. 3.—School of Computer Science and Electronic Engineering, University of Essex, Colchester CO4 3SQ, UK. 4.—e-mail: etiras@anadolu.edu.tr Molecular beam epitaxy-grown In x Ga 1x N/GaN samples with indium fraction x ranging between 0.44 and 0.784 were studied by pulsed current–voltage (I–V) measurements at 1.7 K. The drift velocity, electron mobility, and elec- tric-field-dependent power loss per electron were determined from analysis of the data. The drift velocity increased linearly while the electron mobility re- mained constant with increasing electric field. Power balance equations were used to obtain the power loss per electron as a function of the applied electric field in the range of 0 kV cm 1 to 230 kV cm 1 . The results showed that the power loss per electron increased in the x range of 0.44 to 0.66, then slowly decreased in the x range of 0.66 to 0.784. The results obtained for the dependence of the power loss on the electron temperature are compared with current theoretical models for the power loss in two-dimensional (2D) semi- conductors, which include both piezoelectric and deformation potential scat- tering. For all samples, the energy relaxation of electrons is dominated by acoustic phonon emission via piezoelectric interaction. Key words: Power loss, energy relaxation, indium gallium nitride, mobility, drift velocity INTRODUCTION Group III nitrides have attracted much attention because of their potential application in optical and electronic devices. 1,2 In particular, In x Ga 1x N/GaN alloys have been found to be excellent light emitters for photon energies ranging from 0.7 eV to 3.4 eV, opening the way for applications in quantum-well- based optical devices with emission covering the ultraviolet to red spectral regions. Early measure- ments of InN samples grown by sputtering tech- niques showed a direct bandgap of 1.9 eV to 2.05 eV. 3,4 Recently, following a drastic improve- ment in the growth technique, this value has been updated to 0.7 eV to 1.1 eV for thin films grown by molecular beam epitaxy (MBE) on sapphire (alu- minum oxide) using an AlN or GaN buffer layer. 5–7 However, detailed understanding of the fundamen- tal optical and electronic properties of InN-based structures, which is required for design and development of devices based on high-quality group III nitrides, is far from exhaustive. Nonelectrical or optical interactions can produce unstable free carriers in semiconductors. The extra energy gained by the electron or hole is consumed by interactions with optical and acoustic phonon lattice vibrations. Comparison of experimental results with theoretical studies should provide indirect information about a carrier’s energy distri- bution function. Therefore, an electron temperature (T e ) higher than the lattice temperature (T L ) is often considered to be the only variable parameter in the Maxwell or Fermi–Dirac distribution. 8–13 In addi- tion, deviations from Ohm’s law at intermediate and high electric fields indicate that the carriers gain extra energy. 8–13 The average power gained per carrier due to an applied electric field is given by P ¼ elF 2 ; ð1Þ where F is the applied electric field, e is the elementary charge, and l is the carrier mobility. If the energy gained by electrons in the electric field is (Received July 21, 2015; accepted November 11, 2015; published online December 9, 2015) Journal of ELECTRONIC MATERIALS, Vol. 45, No. 2, 2016 DOI: 10.1007/s11664-015-4250-2 Ó 2015 The Minerals, Metals & Materials Society 867