Capacitance response due to recharging of extended defects attached to the edge of the space charge region of the Schottky diode



Extended defects with a high local density of electronic states like quantum wells, quantum dots, dislocations and precipitates build an own space charge region (SCR) of finite sizes in their close vicinity. When the defects are situated close to the Schottky diode SCR the overlapping of the potentials of the diode and of the defects results in the creation of a potential minimum. In this work, a new theoretical treatment of this situation based on an analytical/numerical solution of Poisson equation taking into account the presence of free electrons is presented. It is shown that small but noticeable lowering of the extended defect states occupancy with electrons is accompanied with unexpectedly large capacitance changes that exhibit a maximum at a certain distance between the defect and the diode SCR. The magnitude of the capacitance changes at the maximum is practically the same as the changes within the diode SCR due to complete refilling of the defect from its equilibrium occupancy to zero. The origin of the capacitance maximum can be qualitatively explained as an effect of “touching/detouching” of the SCR of the defect and that of the diode. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)