Radiation Produced Trapping Effects in Devices-Invited Paper

The effects of radiation-produced majority carrier traps in junction space-charge regions are reviewed. The nature of trapping states is discussed, and defect states in the upper half of the bandgap are shown to be dominant in p+n junctions. A number of experimental methods for determining trap parameters are examined, and the results of various experiments compared. Three important levels are found at energies 0.48, 0.38, and 0.2 eV below the conduction band edge. Best estimates of the electron capture cross sections are 2 × 10-14, 4 × 10-15, and 1 × 10-19 cm2 respectively. These levels give rise to frequency dependent small-signal device parameters in junction field-effect transistors, as well as time dependent parameters for large signals. Only very slight trapping effects are found in enhancement-mode MOS transistors; however the effects should be much larger in depletion-mode devices. Trapping effects restrict the application of variable capacitor diodes.