Growth and Characterization of a-plane In 0.2 Ga 0.8 N/ GaN hetrostructures on r-Sapphire
- PDF / 1,049,808 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 80 Downloads / 219 Views
Growth and Characterization of a-plane In0.2Ga0.8N/ GaN hetrostructures on r-Sapphire Shruti Mukundan1, Lokesh Mohan1, Greeshma Chandan1, Basanta Roul1, 2, S.B.Krupanidhi1,* 1 2
Materials Research Centre, Indian Institute of Science, Bangalore, India. Central Research Laboratory, Bharat Electronics, Bangalore, India
E-mail: [email protected] ABSTRACT Non-polar a-plane InGaN films were grown on a r-plane sapphire substrate by plasma assisted molecular beam epitaxy (PAMBE). The growth temperature and Indium flux were varied to optimize the desired composition of In0.23Ga0.77N on the (11-20) a-plane GaN epilayer grown on a (1-102) r-plane sapphire substrate. The structural, morphological and optical properties of the optimized composition have been studied. It was found that highly a-axis oriented InGaN epilayers with no phase separation can be grown at 540 °C with In/Ga flux ratio of 0.72. The composition of indium incorporation in single phase InGaN films was found to be 23% as estimated by high resolution X-ray diffraction. The room temperature band gap energy of single phase InGaN layers was determined by photoluminescence measurement and found to be around 2.56 eV.
INTRODUCTION Greatness of GaN belonging to the III-nitride family, lies in its wide direct bandgap of 3.4 eV [1]. Band gap of InN is now accepted as 0.7 eV as opposed to previously believed 1.3 eV [2]. This has resulted in the formation of InGaN material system whose band gap can span the whole of solar spectrum (0.7-3.4 eV), even more interesting is that the band gap is direct for the entire material system [3]. It has been studied intensively over the last few years for its possible applications in optoelectronic and electronic devices such as light emitting diodes, laser diodes and high temperature/ high power electronics. A concern with these III-nitride materials is the intrinsic and strong polarization fields resident in the crystal lattice. To overcome such polarization effect, substrates oriented in non-polar directions i.e. (10-10) m-plane or (11-20) aplane are preferred. Devices grown in these orientations are receiving a lot of focus due to this enhanced behavior [4-5]. The large difference in interatomic spacing between GaN and InN (11%) can give rise to a solid phase miscibility gap which makes the growth of InGaN very challenging, especially for higher concentration of indium in the ternary film (>20%) [6]. As the indium content in the InGaN alloy increases, the material quality degrades due to phase separation, inhomoginity of solid solution and indium metal droplets [7]. In the present work, we report successful growth of a single phase nonpolar In0.23Ga0.77N film grown on GaN/ r-sapphire along with structural and optical characterization of the same.
EXPERIMENT InGaN films of thicknesses around 200 nm were grown on 200 nm a-GaN (11-20) / rAl2O3 (1-102) by Omicron Nanotechnology plasma-assisted MBE system. The sapphire substrate was degreased by first boiling in trichloroethylene for 5 minutes and then dipped in acetone and meth
Data Loading...
