Title : n-ZnO/p-GaN LED Heterostructure Near UV-Blue LED with AlN Electron Blocking Layer
Abstract:
High quality single crystalline n-type ZnO films (~200 nm) were grown on top of AlN/GaN heterostructures using r.f. magnetron sputtering under 25 W, 50 W and 100 W sputtering powers. The AlN and p-type GaN layers were deposited by metalorganic chemical vapor deposition (MOCVD). From X-ray diffraction measurements, the samples exhibited the (0 0 0 l) peaks corresponding to both ZnO, GaN and AlN monocrystalline layers. As the sputtering power increased, the grain size increased and the dislocation density decreased. This result is supported by the rms values obtained on the ZnO layers from AFM results. In addition, photoluminescence peaks of ZnO at 372 nm, 375 nm and 380 nm were seen as dependent on the sputtering power. We have used an AlN electron blocking layer between ZnO and GaN films to improve the electroluminescence from the n-ZnO side. Room temperature electroluminescence (EL) of the LEDs demonstrated near UV-blue emission consisting of predominating peaks centred at 405 nm, 390 nm and 380 nm for the device with ZnO deposited at 25 W, 50 W and 100 W sputtering powers, respectively. Moreover, the I-V curves of the LEDs showed a rectifying behavior with 6.8 V, 6.4 V, 5.2 V threshold voltages for 25 W, 50 W and 100W values.
Keywords: ZnO; Nitrides; Magnetron Sputtering; Light Emitting Diode; Etching; MOCVD; e-beam evaporation.
