Reproducible Sb-doped p-type ZnO films were grown on n-Si (100) by electron-cyclotron-resonance-assisted molecular-beam epitaxy. The existence of Sb in ZnO:Sb films was confirmed by low-temperature photoluminescence measurements. An acceptor-bound exciton (A°X) emission was observed at 3.358 eV at 8 K. The acceptor energy level of the Sb dopant is estimated to be 0.2 eV above the valence band. Temperature-dependent Hall measurements were performed on Sb-doped ZnO films. At room temperature, one Sb-doped ZnO sample exhibited a low resistivity of 0.2Ωcm, high hole concentration of 1.7×1018cm−3 and high mobility of 20.0cm2∕Vs. This study suggests that Sb is an excellent dopant for reliable and reproducible p-type ZnO fabrication.

We investigated photoluminescence ͑PL͒ from reliable and reproducible Sb-doped p-type ZnO films grown on n-Si ͑100͒ by molecular-beam epitaxy. Well-resolved PL spectra were obtained from completely dopant-activated samples with hole concentrations above 1.0ϫ 10 18 cm −3. From free electron to acceptor transitions, acceptor binding energy of 0.14 eV is determined, which is in good agreement with analytical results of the temperature-dependent PL measurements. Another broad peak at 3.050 eV, which shifts to lower energy at higher temperatures, indicates the formation of deep acceptor level bands related to Zn vacancies, which are created by Sb doping.

ZnO p-n homojunction light emitting diodes were fabricated based on p-type Sb-doped ZnO∕n-type Ga-doped ZnO thin films. Low resistivity Au∕NiO and Au∕Ti contacts were formed on top of p-type and n-type ZnO layers, respectively. Au∕NiO contacts on p-type ZnO exhibited a low specific resistivity of 7.4×10−4Ωcm2. The light emitting diodes yielded strong near-band-edge emissions in temperature-dependent and injection current-dependent electroluminescence measurements.

Antimony (Sb) doping was used to realize p-type ZnO films on n-Si (100) substrates by molecular beam epitaxy. These samples were fabricated into p-n heterojunction diodes. p-type behavior of Sb-doped ZnO was studied by carrying out I-V and capacitance-voltage (C-V) measurements. I-V curves showed rectifying behavior similar to a p-type Schottky diode with a turn-on voltage around 2.4V, which is consistent with the Schottky barrier of about 2.2V obtained from C-V characterization. Good photoresponse in the UV region was obtained, which further proved that Sb doping could be used to fabricate p-type ZnO for photodetector and other optoelectronic applications.

Phosphorus-doped p-type ZnO films were grown on r-plane sapphire substrates using molecular-beam epitaxy with a solid-source GaP effusion cell. X-ray diffraction spectra and reflection high-energy electron diffraction patterns indicate that high-quality single crystalline (112¯0) ZnO films were obtained. Hall and resistivity measurements show that the phosphorus-doped ZnO films have high hole concentrations and low resistivities at room temperature. Photoluminescence (PL) measurements at 8 K reveal a dominant acceptor-bound exciton emission with an energy of 3.317 eV. The acceptor energy level of the phosphorus dopant is estimated to be 0.18 eV above the valence band from PL spectra, which is also consistent with the temperature dependence of PL measurements.

ZnO -based p-n homojunctions were grown using molecular-beam epitaxy. Sb and Ga were used as dopants to achieve the p-type and n-type ZnO, respectively. The mesa devices were fabricated by employing wet etching and standard photolithography techniques. Al∕Ti metal was deposited by electron-beam evaporation and annealed to form Ohmic contacts. Current-voltage measurements of the device showed good rectifying behavior, from which a turn-on voltage of about 2V was obtained. Very good response to ultraviolet light illumination was observed from photocurrent measurements.

Phosphorus-doped ZnO films were grown by molecular-beam epitaxy with a GaP effusion cell as dopant source. Three growth regions were identified to obtain ZnO films with different conduction types. In the oxygen-extremely-rich region, phosphorus-doped ZnO films show n-type conduction with dominant donor-bound excitons (DX0) in the low-temperature photoluminescence (PL) spectra. In the oxygen-rich region, a growth window was found to generate p-type ZnO films. The PL spectra show evident competitions between DX0 and acceptor-bound excitons (AX0). In the stoichiometric and Zn-rich region, ZnO films are n-type with dominant DX0 emissions. Thus, phosphorus doping is amphoteric, having the tendency to form both donors and acceptors in ZnO.

Heterojunction light emitting diodes (LEDs) were fabricated by making Au∕Ni top Ohmic contacts on Sb-doped p-type ZnO film with low specific contact resistivity and Al∕Ti back Ohmic contacts on n-type Si substrate. Near-band edge and deep-level emissions were observed from the LED devices at both low temperatures and room temperature, which is due to band-to-band and band-to-deep level radiative recombinations in ZnO, respectively. The electroluminescence emissions precisely match those of photoluminescence spectra from Sb-doped p-type ZnO, indicating that the ZnO layer acts as the active region for the radiative recombinations of electrons and holes in the diode operation.