ANALYSIS OF THE THERMAL CONDITIONS OF PULSE IMPACT AVALANCHE TRANSIT-TIME DIODES

The nonstationary problem of the thermal process for the pulse mode of impact avalanche transit-time diodes is solved. The one-dimensional thermal model of such diodes, which takes into account the heterogeneity of the thermal power distribution and the heat spreading along the heat sink in the operating temperature range, is considered. The numerical calculation results of the average temperature of the active layer and the thermal resistance on the pulse parameters, as well as on the geometric and thermophysical diode parameters, are presented. Maximum output powers of semiconductor devices are restricted, first of all, by heating of the active regions of semiconductor up to the temperatures enough for the thermal destruction of these regions. Use of the pulse mode allows to increase the instantaneous values of the microwave device output capacity; and the smaller pulse duration, the greater this increase. Rigorous solution of the nonstationary thermal problems for the specific structures is mathematically extremely complicated and can be found with computer only. For a number of simplified models the analytical time dependences of the active region temperature of impact avalanche transit-time (IMPATT) diodes are obtained (1, 2). However, these dependences are useless for strictly quan- titative estimates, since they do not take into account the essential factor, namely, the temperature variation of the thermal conductivity in the opera- ting temperature range 300-500 K, which is quite substantial. In the present paper the determination of the temperature characteristics of IMPATT diodes is carried out using the analytical approach (3). Results of such analysis comprise a wide range of parameters and are found to be comparable with experimental study results of the temperature characteristics.