Radiation Induced Hump Structure in the I-V Characteristics of Esaki Diodes

Abstract

Well-defined hump structure is produced in the excess current region of Si, Ge, and GaAs Esaki diodes by irradiation with two MeV electrons, when the I-V characteristic is observed at low temperature. Si diodes develop humps at 0.35, 0.63, and 0.90 V at irradiation temperatures from 77° to 300°K. Ge diodes show humps at 0.23 and 0.51 V when irradiated at low temperature, but only a hump at 0.23 V after room temperature irradiation. GaAs diodes show humps at approximately 0.4 and 0.9 V. Diodes of approximately one mA peak current generally show hump current changes comparable to the peak current with an integrated flux of approximately 1017 electrons/cm2. On the basis of a simple model postulating direct tunneling of electrons from the conduction band of the n material to defect levels in the p material, generally good agreement is found with previous work on location of defect levels in Ge and Si. The technique shows promise as a tool for locating deep lying defect levels in the less thoroughly studied compound semiconductors. The first two humps in Si anneal from slightly above room temperature to above 250°C. The third hump does not anneal significantly to 250°C. The two humps produced on low temperature irradiation of Ge both anneal rapidly just below 0°C, while a third hump at 0.60 V appears in this temperature range. Hump structure produced or remaining in Ge at room temperature is stable to above 100°C, where anneal takes place with second-order kinetics and apparently goes to completion.