Electrical Properties of Submicronic Emitters. Application to the Case of Solar Cells and Subnanosecond Hyperfrequency Transitors.

摘要

This paper aims at specifying the importance of the main mechanisms which determine the electrical properties of doped p-n junctions until the degenerescence, and of depths below one micron. A concrete aim of this work is the study of the efficiency of injection of the emitter-base junction of subnanosecond bipolar transitors, as also the electrical characteristics of solar cells. These devices are made of silicon. In a first part, the photovoltaic effect, and the technology of solar cells are briefly reviewed; the results of the simple theory of the p-n junction are recalled. In the following part, the contribution of the different regions of the device to the dark current are explained. The relative values of hole and electron currents are discussed, taking into account the values of the main physical parameters in the devices: depth of the junction, concentration gradient in the diffused region, life-time of minority carriers in the emitter, concentration of acceptors in the base. This will allow to point out the parameters of which modifications would lead to a lower value of the dark current; thus, would involve a more important value of the open-circuit voltage. In the third part, a new method to determinate the impurities concentration in the diffused region in the vicinity of the junction, is presented. The emitter regions of the submicronic devices being strongly doped, the performance of these devices are expected to be influenced by a very short life-time of the AUGER type and by a reduction of the width of the energy gap. In the fourth part, the main models of reduction of the width of the energy gap proposed in the literature, are discussed. The fifth part sums up the results of calculation of gain on hyperfrequency NPN type transistors according to the models for strong doping previously discussed. (ERA citation 09:032851)