Charge transport, trapping and electroluminescence in erbium doped a-Si:H/n-Si light-emitting heterodiodes

In this paper we explore the charge trapping and transfer properties of a-Si:H(Er)/n-Si light-emitting heterodiodes. Using the methods of thermally activated current (TAC) spectroscopy and current–voltage (I–V) characteristics in the temperature range from 80 to 350 K the mechanisms of charge transfer have been determined. It has been shown, that at small reverse voltages (below 3 V) and low temperatures (below 220 K) the charge transfer can be described by variable-range hopping conductivity mechanism. Increasing the voltage above 3 V leads to the establishment of multistep recombination tunneling process with hole participation, that is described by I=I0 exp(V/V0) exp(T/T0). At temperatures above 220 K a space charge limited current together with thermally activated tunneling mechanisms I=I0 exp(−Ea/kT) exp(V/V0) are manifested. It has been demonstrated that an increase of the hole injection into a-Si:H(Er) film by changing of the n-type Si substrate with a p-type one results in an increased electroluminescent efficiency of the light-emitting devices.