Assessing the performance and reliability of GaN based electronics via optical and electrical methods

Abstract

Gallium nitride (GaN) based electronics have shown great potential for RF devices and power electronics. Its superior material properties have enabled the fabrication of high frequency and high voltage devices. Under high power operational conditions, significant localized Joule heating occurs near the drain side edge of the gate which can have detrimental effects on the device. The quantification of performance parameters such as the gate junction temperature is thus necessary to accurately assess the device's quality and lifetime. Until now Raman thermometry has shown to be the most accurate method to estimate the junction temperature. This method, however, is limited to a point measurement and sometimes may be limited by its optical access. Furthermore, the ability to monitor the transient temperature rise under pulsed conditions has not been yet fully developed. This thesis presents advanced methods for in-situ transient temperature measurements, using gate resistance thermometry, and temperature mappings across GaN based electronics via transient thermoreflectance imaging (TTI). A combination of experimental and numerical analysis is used to achieve this. The methods are applied to lateral HEMTs, vertical PIN diodes and cross sectional HEMTs. The limitations of the current techniques are discussed and contrasted.