Study of conduction mechanism at nanoscale in (Al,Ga)N heterostructures

Gallium nitride (GaN) is anticipated to be the next-generation power semiconductor. Due to their superior properties including wide bandgap, high electron mobility, resistance to thermal degradation and high breakdown field, GaN-power devices significantly outperform Si-based power chips. Such devices are composed of carefully tailored complex (Al,Ga)N heterostructure layers, which go down to only few nanometers in thickness. As there is an immediate need to tackle issues related to defects induced during growth/device processing, dopant activation and device reliability impeding the development of GaN devices, this internship explores the use of scanning probe microscopy (SPM) to address such concerns.

The goal of this internship is to identify and gain understanding of the conduction mechanism at the nano-size contact formed between a metallic or a highly-doped diamond probe sharp tip and differently doped (Al,Ga)N layer. This is crucial for revealing the role of charged defects like dislocations, which are typically present (10⁸ to 10⁹ cm^-2), and how they affect the device performance. This will be correlated with other macroscopic electrical characterization techniques including Current-Voltage and Capacitance-Voltage measurements. In the next step, the effect of high pressure reaching up to tens of GPa at the SPM probe tip/GaN contact will also be studied, which will serve as the stepping stone towards realizing scanning spreading resistance microscopy for dopant quantification in (Al,Ga)N heterostructures. With the guidance of his supervisor, data interpretation and analysis will also be a major part of the thesis/internship. As such, the student will be guided in design of the experiment and understanding the resulting experimental data. A good command of English is required.