Strain engineered N-Polar relaxed InGaN films using porous layers; targeting deep mm-wave applicatio
Abstract
Gallium Nitride (GaN) semiconductor in its Nitrogen-polar (N-polar) orientation has demonstrated exceptional RF power performance at, the device level in the mm-wave frequency range, upto 100 GHz. Compared to other compound semiconductors, GaN based high electron m,obility transistors or HEMTs utilize the large critical electric fields due to wide band-gap and high electron mobility of this mate,rial to demonstrate unmatched output power, gain and efficiency for wireless transmitter applications. Despite these advantages, bey,ond 100 GHz, these devices are attaining output power and gain saturation due to the relatively high electron effective mass of 0.2m,e in the GaN material, compared to, for instance, 0.047me for that of InGaAs on InP. In addition to device dimension scaling, effort,s to enhance the velocity of the charge carriers is crucial to increase the operating frequency of these devices, to break through t,his performance saturation at frequencies beyond 100 GHz. Our objective is to demonstrate lowering of electron effective mass in GaN, HEMTs utilizing strain engineering, to enable electron velocity enhancement. Taking inspiration from the strain engineering based e,ffective mass lowering of electrons and holes in Silicon, first demonstration of effective mass lowering of electrons in GaN channel,s is targeted. Unfortunately, GaN is a ceramic like hard material, with both hardness and elastic modulus, twice that for Silicon. H,ence, strain engineering in GaN is substantially challenging to demonstrate. The utilization of porous nitride semiconductors is p,roposed in the context of strain engineering. Use of porous semiconductors have been demonstrated in LASER structures serving as mir,rors or an optical component due to the difference in their refractive index in comparison to a bulk or non-porous semiconductor. Th,e study of the mechanical properties of these porous layers, has revealed a reduction in mechanical stiffness, presenting a unique o,pportunity for the use of these films as relatively flexible underlayers. A novel approach to utilize these porous semiconductors to, stretch the lattice constant of GaN material is proposed. The larger in-plane lattice constant of GaN will increase the curvature o,f the conduction band in the energy-momentum diagram, resulting in a higher electron mobility/velocity in the channel. The enhanced,electron velocity in combination with aggressively scaled devices, will lead to a higher operating frequency of RF power devices. Ga,N based RF power devices are crucial for enabling many military applications such as radars and electronic warfare systems, wherein,high output power, reduced form factor and efficient heat management are highly prioritized. With Navys support, the continuous dev,elopment of Nitrogen-polar GaN was the 2nd wave in GaN electronics and changed the landscape of RF power devices as we know it, with, breakthrough device level performances until 100 GHz. With the enhancement of a fundamental material property that is, the electron, effective mass lowering, the 3rd wave in GaN electronics is imminent. The lower effective mass of electron will improve: the RF dev,ice efficiency with reduced power consumption; and reduce the form factor of the devices due to high frequency operability beyond 10,0 GHz, resulting in breakthrough RF performance of N-polar transistors. These transistors, with suitable matching networks surroundi,ng it, will be the frontiers in next generation electronic systems in the US defense sector. Approved for Public Release
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 01, 2022
- Source ID
- N000142212267
Entities
People
- Shubhra S Pasayat
Organizations
- Office of Naval Research
- United States Navy
- University of Wisconsin System