Effect of Pressure on the energy band gaps of In x Ga 1-x N and In x Al 1-x N
- PDF / 74,477 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 25 Downloads / 207 Views
L11.25.1
Effect of Pressure on the energy band gaps of InxGa1-xN and InxAl1-xN Z. Dridi 1, 2, B. Bouhafs 1, 2, and P. Ruterana 1 1 LERMAT, FRE 2149-CNRS, ISMRA, 6 Boulevard Marechal Juin, 14050 Caen Cedex, France. 2 Modelling and Simulation in Materials Science Laboratory, Physics Department, University of Sidi Bel-Abbes, 22000 Sidi Bel-Abbes, Algeria. ABSTRACT Using a first-principles method, we study the effect of pressure on the band gap energies of wurtzite InxGa1-xN, and InxAl1-xN. The fundamental band gap energies are direct and increase rapidly with pressure. The pressure coefficients vary in the range of 19.8-24.8 meV/GPa for InxGa1-xN, and 16.7-20.7 meV/GPa for InxAl1-xN; they depend on alloy composition with a strong deviation from linearity. The band gap bowing of the InGaN increases continuously with pressure while those of InAlN strongly decreases at p=14 GPa.
INTRODUCTION The development of light-emitting diodes and laser diodes operating in green and blue spectral regions has stimulated the study of the III-nitrides GaN, InN, AlN and their ternary alloys InxGa1xN, and Inx Al1-xN. The first motivation comes from their large and direct band gaps 3.5 eV [1] for GaN, 1.89 eV [2] or 0.8 eV by recent PL measurement [3, 4] for InN, and 6.28 eV [5] for AlN, which would allow to cover an exceptionally large spectrum. Not withstanding an important research activity for the last decade on these compounds, a number of their properties are not yet well understood or agreed on such as the band gap bowing parameter of the ternary alloys [6, 7]. Moreover, the band-gap pressure coefficients are not well known. For the InGaN alloys, the available experimental studies reported pressure coefficients for a limited composition range: from 0.04 to 0.14 [8, 9, 10]. These values are almost independent of the composition. Theoretically, to our knowledge only the recent work of Perlin et al. [11] reported the pressure coefficients of InxGa1-xN, by means of the full-potential LMTO method. An important dependence of the pressure coefficient on the alloy composition was shown. For InxAl1-xN, no results are available. The InGaN alloys are and will be more and more necessary in LEDs, LDs, as well as in transistors based strained heterostructures. Therefore it is important to know the pressure dependence of their band gap with a given mole fraction in order to calculate the band alignment for designing and optimizing such devices. The InxAl1-xN alloy, exhibits the largest variation in the band gap and it is a candidate for less lattice mismatched confinement layers in optical devices. In the following, we use the full-potential linear augmented plane-wave (FP-LAPW) method, to study the behavior of the band gap under pressure for wurtzite InxGa1-xN, and InxAl1-xN, and to investigate the band gap bowing dependence on pressure.
L11.25.2
DETAILS OF CALCULATION The calculations are performed using the density-functional theory within the local density approximation (LDA) [12], as implemented by the non-scalar relativistic full potent
Data Loading...
