Electroluminescent and carrier transport mechanisms of MgxZn1−xO∕Si heterojunctions

Abstract

Mg x Zn 1 − x O (x≈0.19) films were, respectively, deposited by reactive sputtering on the heavily arsenic-doped (n+), lightly phosphorus-doped (n−), heavily boron-doped (p+), and lightly boron-doped (p−) silicon substrates. The sputtered MgxZn1−xO films were n-type with an electron concentration of 4.1×1017cm−3. Moreover, the energy-band gap of the MgxZn1−xO films was determined to be ∼3.67eV. The MgxZn1−xO∕n−-Si and MgxZn1−xO∕p−-Si heterojunctions showed rectifying behavior to different degrees while the MgxZn1−xO∕n+-Si and MgxZn1−xO∕p+-Si heterojunctions did not possess rectifying function. The MgxZn1−xO∕n+-Si heterojunction exhibited UV near-band-edge and visible defect-related electroluminescence (EL) under the forward bias but only visible EL under reverse bias; while the MgxZn1−xO∕n−-Si heterojunction only emitted relatively weak UV and visible EL under the forward bias. On the other hand, the MgxZn1−xO∕p+-Si heterojunction was electroluminescent in the visible region under the forward bias while in both the UV and visible regions under the reverse bias; and the MgxZn1−xO∕p−-Si heterojunction did not exhibit detectable EL under either forward or reverse bias. The mechanisms of the EL and carrier transport for the above-mentioned heterojunctions have been tentatively explained in terms of their energy-band structures.