In this work, a new method for failure analysis of electronic components, high speed camera, is used to investigate burnout failure location of GaN HEMTs under RF overdrive stress. Based on the high speed camera system and the RF test system, we can filter out most of the burn flashes, and clearly locate the weak parts of devices. To further explain the burnout mechanism, a long-term (100 h) RF overdrive stress experiment was carried out and the significant degradation was observed. The drain-source current decreases and the threshold voltage drifts forward. These phenomena show that the degradation of RF overdrive stress is based on hot electron effect (HEE), which is related to the electric field. Besides, Electroluminescence (EL) tests are used and the non-uniform but strong luminescence characteristics of the gate were found, which indicates the strong electric field is the main cause of burnout. We also explore the correlation between burnout and ambient temperature. It was found that the influence of ambient temperature on the burnout was limited. At last, a TCAD simulation is carried out to confirm the temperature and electric field distribution in the device when burnout. It can be found that the electric field inside the device exceeded the breakdown electric field of GaN, which further proves that the burnout caused by RF overdrive is mainly due to electric field rather than temperature.

In order to describe electron transport properties in inversion layer of strained Si/Si1-xGex nMOSFETs, a new analytic electron mobility model is proposed. The model not only takes into account the effect of germanium(Ge) content on phonon scattering-limited mobility and surface roughness-limited mobility, and but also includes the degradation effect of strained Si film thickness and temperature on the device mobility. For various Ge content and a wide range of normal electric field, temperature and strained Si film thickness, the model provides good agreement with the experimental data in references. In addition, the model can be expressed using the analytical expression and can be easily included in the device simulator.

SiGe heterojunction structure much improves the performance of PnP HBT (heterojunction bipolar transistor), which focus on the impact of Ge component distribution in the base on the current gain and characteristic frequency . The triangular distribution in the base, including zero-doping and non-zero-doping at the starting point, will form a Ge-gradient acceleration filed for the minority carriers in the base to reduce the base transport time and increase current density and working frequency. Extend Ge to the collector region to eliminate the effect of the valence band spike barrier at the collector junction, further improving the performance of the pnp HBT. By the simulations and optimizations in this paper, the and of pnp SiGe HBT improves evidently, and the results can be referenced in the design of SiGe devices and circuits.