Relaxed InGaN films on ZnO for RF applications
Abstract
Relaxed InGaN films on ZnO for RF applications Enabling relaxed InGaN buffer layers is not only interesting for optoelectronic application; it is extremely attractive for electronic devices as well. The dominant factor in fT in a well-designed high electron mobility transistor (HEMT) with reduced parasitic capacitances is the transit time in the channel given by the ratio of gate length and the average electron velocity in the channel. A combination of higher electron velocity and large bandgap is needed for high-frequency and high-power applications. One way of achieving this is using relaxed InGaN as the channelmaterial which provides a reduced electron effective mass, critical in reducing electron scattering and enhancing electron velocity. Relaxation of the InGaN channel is required since an InGaN channel coherently grown on GaN substrate does not provide an effective mass commensurate with the In mole fraction.Here, we propose developing relaxed In0.2Ga0.8N buffers on ZnO. They both have Wurtzite crystal structure. Furthermore, based on Vegards law, in-plane lattice constant of In0.2Ga0.8N is 3.25 nm which is perfectly matched to that of ZnO. This allows growth of high quality relaxed In0.2Ga0.8N on ZnO. Also, PAMBE is a relatively low temperature growth technique which should suppressthe formation of unwanted In2O3 interlayer because of reaction between O and InGaN at the interface enabling smooth growth on these lattice-matched but chemically dis-similar materials. We will systematically study the growth of InGaN films on ZnO substrates using plasma-assisted molecular beam epitaxy (PAMBE). We will systematically study Si doping of relaxed InGaN films. We will use temperature dependent Hall measurements to measure electron density and mobility in relaxed InGaN films, and compare that with those in strained InGaN films grown on GaN for similar doping concentrations.We anticipate that the polarity of InGaN films (Ga-polar vs N-polar) will be directly related to the polarity of the ZnO face that the layer is grown on. Ga-polar resulting from growth on the Zn-face and N-polar on the O-face ZnO substrates. We will design and fabricate InGaN-(Al,Ga)N high electron mobility transistors on both polarities of InGaN. We will also study the 2DEG charge density and mobility as a function of barrier (AlGaN) composition and thickness.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 27, 2018
- Source ID
- N000141812703
Entities
People
- Elaheh Ahmadi
Organizations
- Board of Regents of the University of Michigan
- Office of Naval Research
- United States Navy