The development of a system for characterization of deep traps by transient capacity

A method is presented for characterization of defects in semiconductor devices in terms of deep traps. The variations in the transition capacity of a heterojunction device with deep traps when the applied voltage is varied abruptly is examined. The response follows an exponential law when the trap density is less than the density of dopant atoms. An analytical model is developed to described the variations, taking into account the structural characteristics of the device and the applied voltages. Measurement techniques to be used are investigated in terms of sensitivity, power of resolution, and the SNR. The dual gate procedure, adapted for numerical solution, is found to be the best available method. The transient is identified and localized by a number of discrete points. Test results showed that traps could be characterized with emission speeds less than 50/sec at 100 K and higher than 1.4/sec at 400 K, with an amplitude sensitivity of 5 x 10 to the -15th. The technique is concluded useful for identifying the defects introduced into semiconductors by the manufacturing process, and also defining their effects in terms of the end use.