I think that this link can help you about High Temperature Reverse Bias.

http://electroiq.com/blog/2013/09/high-temperature-reverse-bias-reliability-testing-of-high-power-devices/

Good luck!

HTRB  high source-drain voltage and temperature along with long lasting temperature gradients are initiating electro-migration flow of defects, while the temperature gradient creates a stationary phonon flow that can drag defects.

It create quite favorable conditions for electrically active impurities and other defects migration along field and temperature gradients, which can lead to carries' mobility degradation in the field depletion structures. Hence, changes in carriers' mobility according to the CMOS device physics initiate respective changes (drift) in the Vth voltage.   

High temperature reverse bias reliability testing of high power devices

Power device characterization and reliability testing require instrumentation capable of sourcing higher voltages and more sensitive current measurements than ever before.

Silicon carbide (SiC), gallium nitride (GaN), and similar wide bandgap semiconductor materials offer physical properties superior to those of silicon, which allows for power semiconductor devices based on these materials to withstand high voltages and temperatures. These properties also permit higher frequency response, greater current density and faster switching. These emerging power devices have great potential, but the technologies necessary to create and refine them are less mature than silicon technology. For IC fabricators, this presents significant challenges associated with designing and characterizing these devices, as well as process monitoring and reliability issues.

Before wide bandgap devices can gain commercial acceptance, their reliability must be proven and the demand for higher reliability is growing. The continuous drive for greater power density at the device and package levels creates consequences in terms of higher temperatures and temperature gradients across the package. New application areas often mean more severe ambient conditions. For example, in automotive hybrid traction systems, the temperature of the cooling liquid for the combustion engine may reach up to 120°C. In order to provide sufficient margin, this means the maximum junction temperature (TJMAX) must be increased from 150°C to 175°C. In safety-critical applications such as aircraft, the zero defect concept has been proposed to meet stricter reliability requirements.

Thanks all for the answer. Are there any difference in Degradation model for Trench MOSFET compared to Planar MOSFET?