High mobility ultrathin ZnO p–n homojunction modulated by Zn 0.85 Mg 0.15 O quantum barriers

The adding of ZnMgO asymmetric double barriers (ADB) in p-ZnO: (Li, N)/n-ZnO homojunction affects the p–n junction device performance prominently. Two different homojunctions are fabricated on Si (100) substrates by pulsed laser deposition; one is the traditional p-ZnO: (Li, N)/n-ZnO homojunction with different thicknesses named as S 1 (250 nm) and S 2 (500 nm), the other is the one with ADB embedded in the n-layer named as Q (265 nm). From the photoluminescence spectra, defect luminescence present in the S-series devices is effectively limited in the Q device. The current–voltage curve of the Q device shows Zener-diode rectification property because the two-dimensional electron gas tunnels through the narrow ZnMgO barrier under a reverse bias, thus decreasing the working p–n homojunction thickness from 500 nm to 265 nm. The ADB-modified homojunction shows higher carrier mobility in the Q device. The electroluminescence of the ZnO homojunction is improved in Q compared to S 2 , because the holes in p-type ZnO (Li, N) can cross the wide ZnMgO barrier under a forward bias voltage into the ZnO quantum well. Therefore, electron–hole recombination occurs in the narrow bandgap of n-type ZnO, creating an ultraviolet light-emitting diode using the ZnO homojunction.