Gate Degradation Model Of The AlGaAs/InGaAs PHEMT

With development of the high technology, high reliability and national defensemodernization of the country communication system，the demand for PHEMT deviceand its circuit is more and more strong. The exposed reliability problems in theapplication of PHEMT device has seriously affected the device’s usage, especially theparameter drift, output power declining, grid breakdown etc. Gate side reliability hasalways been the key factor that cause PHEMT failure and restrict the development ofthe PHEMT reliability. Gate current is always an important indicator to measure thereliability of the gate side. The researches at home and abroad are focusing on thequalitative research of failure mechanism caused by gate current degradation, but theresearch on PHEMT gate current degradation law and the influence on gate currentdegradation corresponding to failure mechanism.Aiming at solving this problem, the PHEMT gate leakage current parameterdegradation model is proposed based on the relationship between volumeconcentration and reaction rate in the degradation process of physical chemistryreaction, and the systematic study has been done theoretically and experimental.Specific content includes the following aspects:1. Based on the relationship between volume concentration and reaction rate inthe degradation process of physical chemistry reaction, the PHEMT gate leakagecurrent parameter degradation model is proposed. From this degradation model, theparameter degradation law and the trend from the physical mechanism can beexplained, the various failure mechanism parameters leads to degradation can bedistinguished, and the time constant and degradation ratio of each failure mechanismcan be quantified.2. Establishing of the failure mechanism of consistency discriminant model.Under the condition of constant accelerated stress, the potential failure mechanism ofthe device could be inspired and became the main failure mechanism for the highexperimental stress level. The failure mechanism also changed and leaded to theineffective accelerated experiments. In this article, the relationship between thedegradation data distribution parameters and consistency of the failure mechanism isdeduced under different stress. The model is theoretically experimental verifiedfinally. 3. Designing and building of online parameter degradation system. In order tofulfill the accuracy of the degradation data in the model and avoid the temperature andcurrent impact experiment error in the parameter degradation experiment, a set ofonline parameter measuring system was designed. With computer as control side andthe international common interface as the foundation of data communication, onlineparameter measuring system can realize electric stress loading and measuring work.4. Establishing the AlGaAs/InGaAs PHEMT gate leakage current parameterdegradation model. Based on the degradation model of the failure mechanism,PHEMT gate leakage current parameter degradation model is proposed. Fromanalyzing the electrical parameter degradation with the time, the failure mechanismthat affect the gate current degradation is obtained, and the time constant anddegradation ratio corresponding to each different failure mechanisms is also obtained.The PHEMT gate leakage current parameter degradation model is successfulestablished.