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The homoepitaxial Si-doped Ga2O3 film prepared by metal–organic chemical vapor deposition (MOCVD) was reported in this paper. The film thickness reached 4.5 microns, a relatively high value for MOCVD. The full width at half maxima of the (002) diffraction plane of the film was 26.3 arcsec, thus showing high crystalline quality. The film showed n−-type properties with a doping concentration of 3.6 × 1016 cm−3 and electron mobility of 137 cm2/V·s. In addition, the element composition and stress state of the film were characterized and analyzed. This indicates that the MOCVD, supporting high-quality, high-precision epitaxy, is promising for Ga2O3 power devices. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV)-emitting n-ZnO/SiO/ p-GaN devices were fabricated by metalorganic chemical vapor deposition. Electroluminescence spectra of the devices were measured from both the n-ZnO and p-GaN sides. It was found that a narrow emission peak centered at ∼391.3 nm was observed from the front side, while three peaks (372 nm, 380 nm, and 390 nm) emerged in the case of testing from the GaN side. To interpret this notable difference, a theoretical mechanism is proposed based on carrier accumulation and injection under forward bias voltage. [ABSTRACT FROM AUTHOR]

In this paper, GaN-based yellow light-emitting diodes (LEDs) were homoepitaxially grown on free-standing (0001) GaN substrates by metal-organic chemical vapor deposition. X-ray diffraction (XRD), photoluminescence (PL), and electroluminescence (EL) measurements were conducted to investigate the structural, optical, and electrical properties of the yellow LED. The XRD measurement results showed that the InGaN/GaN multiple quantum wells (MQWs) in the LED structure have good periodicity because the distinct MQWs related higher order satellite peaks can be clearly observed from the profile of 2θ-ω XRD scan. The low temperature (10 K) and room temperature PL measurement results yield an internal quantum efficiency of 16% for the yellow LED. The EL spectra of the yellow LED present well Gaussian distribution with relatively low linewidth (47–55 nm), indicating the homogeneous In-content in the InGaN quantum well layers in the yellow LED structure. It is believed that this work will aid in the future development of GaN on GaN LEDs with long emission wavelength. [ABSTRACT FROM AUTHOR]

One-dimensional β-Ga 2 O 3 nanostructures were grown at different temperatures on c-plane sapphire substrates by MOCVD using Au as catalyst. The structural, morphological and photoluminescence properties of β-Ga 2 O 3 nanostructures grown at different temperatures were characterized and compared in detail. As the growth temperature was increased, β-Ga 2 O 3 nanostructures exhibited improved crystalline quality and possessed a typical β-Ga 2 O 3 structure with high purity. The β-Ga 2 O 3 nanostructures grown at 750 °C showed intense ultraviolet-blue emission at room temperature. Different morphologies including islands-like, nanowires, nanorods, grain-like structures were obtained depending on the growth temperature. The correlation between the nanostructures shapes and the growth processes was also discussed. [ABSTRACT FROM AUTHOR]

The optical properties of thick InGaN epilayers grown by metal-organic chemical vapor deposition with indium (In) content range from 10% to 42% were investigated. With the increase of In content, the crystal quality of InGaN epilayers significantly degraded, particularly at increasing the edge-type dislocations density for high In content InGaN. Combining high-resolution X-ray diffraction reciprocal space mapping, the splitting of the photoluminescence (PL) peak into several PL bands was found to be caused by compositional fluctuations rather than by the strain effects. Based on the PL and optical absorption spectra, the composition-dependent Stokes shift was observed and a linear relationship between Stokes shift and Urbach tailing energy was established. Additionally, a drop of In incorporation along the growth direction was observed in InGaN epilayers with high In content. Such drop behavior of In incorporation was attributed to the formation of In droplets, which offers a competing pathway for In incorporation by gathering the incoming In atoms hence causing a decrease in the surrounding In incorporation. This will present a broader view about the nature of InGaN alloys with high In content. [ABSTRACT FROM AUTHOR]

Heteroepitaxial growth of conductive Si-doped β-Ga 2 O 3 films on c-plane sapphire substrates by metal-organic chemical vapor deposition (MOCVD) was successfully performed. The effect of Si content on the structural, morphological, electrical and optical properties of Si-doped β-Ga 2 O 3 films was investigated in detail. Distinctive surface morphology evolution of films depending on Si content was observed and presented. The Si-doped β-Ga 2 O 3 films exhibited high transmittance in the ultraviolet-visible regions. The temperature-dependent PL was carried out especially to discuss the photoluminescence properties of Si-doped β-Ga 2 O 3 films. More importantly, the results suggested that the conductivity of heteroepitaxial Si-doped β-Ga 2 O 3 films by MOCVD could be realized and controlled by adjusting the Si content. The minimum resistivity of 1.79×10 −1 Ω·cm was obtained for the films grown under the SiH 4 flow rate of 0.08 sccm. [ABSTRACT FROM AUTHOR]

We fabricated a p-NiMgO:Li/MgO/n-ZnO NWs/ITO heterojunction device and studied its electroluminescence characteristics. Emission from n-ZnO was observed under forward biases. Significantly the random lasing was achieved. Besides, to investigate the characteristics of NiMgO:Li material, we carried out a comparative study on NiMgO:Li and NiO:Li. The p-NiMgO:Li thin films were deposited on c-sapphire substrates by radio-frequency magnetron sputtering using high-purity NiO and MgO ceramic targets. Although, the hole concentration of NiMgO:Li thin film was low compared with the NiO:Li thin film, the electronic mobility and the optical transmittance have obviously improvements. [ABSTRACT FROM AUTHOR]

We utilized in-situ grown SiN x insertion mask to improve the quality of N-polar GaN films on sapphire substrates by metal-organic chemical vapor deposition. The influences of deposition time and position of SiN x insertion mask were studied. Under the optimal SiN x mask growth conditions, the full width at half maximum values of (0002) and (10 1 ¯ 2) XRD rocking curves of N-polar GaN films are decreased to 88″ and 172″, respectively. Simultaneously, Raman spectroscopy measurements reveal that SiN x mask can also reduce the tensile residual stress of N-polar GaN films. In addition, the electrical and optical properties of N-polar GaN films with and without SiN x insertion mask were investigated by temperature dependent Hall and photoluminescence measurements. It is found that N-polar GaN film with SiN x insertion mask has lower background carrier concentration, higher mobility and lower nonradiative recombination rate. [ABSTRACT FROM AUTHOR]

We fabricated the light-emitting diodes (LEDs) consisting of n-ZnO/p-NiO/p-Si heterostructure by using metal-organic chemical vapor deposition (MOCVD) combined with radio frequency (RF) magnetron sputtering. The devices exhibited diode-like rectifying current–voltage characteristics and had a turn-on voltage of 6.8 V. Under forward bias, a prominent broad emission peaked around 400–650 nm was observed at room temperature. The asymmetric electroluminescence (EL) spectra were consisted of two apparent bands, which located at 420 and 495 nm corresponding to the violet and green luminescence, respectively. Furthermore, the mechanism of the light emission was tentatively discussed in terms of the band diagrams of the heterojunction. [ABSTRACT FROM AUTHOR]

Ultraviolet light-emitting diodes (LED) based on n-ZnO/NiO/p-GaN were realized by metal-organic chemical vapor deposition (MOCVD). The devices exhibited diode-like rectifying current–voltage characteristics and had a turn-on voltage of 7.5 V. High quality NiO film as an electron blocking layer inserted between the ZnO and GaN films showed high resistance state with preferred [1 1 1] orientation, which produced a larger ZnO/NiO conduction band offset of 2.93 eV than that of ZnO/GaN (0.15 eV). The electroluminescence spectra of the n-ZnO/i-NiO/p-GaN heterostructure demonstrated that electrons were effectively confined in the ZnO active region, and thus leading to the enhancement of the excitonic emission from the ZnO side. [ABSTRACT FROM AUTHOR]

The β-Ga 2 O 3 films were grown on GaAs (1 0 0) substrates by metal-organic chemical vapor deposition method. The influences of growth pressure on the surface morphology, crystal quality and electrical properties of β-Ga 2 O 3 films were investigated using FE-SEM, XRD and leakage current measurements. It was found that the growth pressure could obviously influence the preferred orientation and growth rate of the β-Ga 2 O 3 films prepared from 2000 Pa to 10,000 Pa. At the growth pressure of 5000 Pa, we obtained β-Ga 2 O 3 film with relatively high resistance. According to the XRD phi-scan results, the in-plane epitaxial relationship could be confirmed as β-Ga 2 O 3 [0 1 0]||GaAs 〈0 1 1〉 and β-Ga 2 O 3 [0 0 1]||GaAs 〈0 1 1〉. In addition, the effect of growth pressure on the parasitic gas-phase reaction was studied to explain the changes of growth rate. [ABSTRACT FROM AUTHOR]

Highlights: [•] The photo assist system can relieve the crystal quality degradation effectively. [•] The Ni and oxygen content have important effect on the characters of the films. [•] The p-NiZnO film can be obtained easily by controlling the Ni and oxygen content. [ABSTRACT FROM AUTHOR]

Abstract: The n-ZnO/i-NiO/n-GaN isotype heterojunction diode was fabricated by metal organic chemical vapor deposition (MOCVD) on the n-GaN/sapphire substrate. The current–voltage (I–V) measurement showed typical rectification characteristics with a turn-on voltage of 2.5V. An ultraviolet emission peak around 363nm was observed from the EL spectra at room temperature. High ultraviolet light extraction efficiency was proved by a superlinear curve of the intensity ratio of ultraviolet to visible emission. The mechanism of electroluminescence has been tentatively elucidated in terms of band diagrams of the heterojunction. [Copyright &y& Elsevier]

Abstract: A p-ZnO:N/n-GaN:Si structure heterojunction light-emitting diode (LED) is fabricated on c-plane sapphire by full metal organic chemical vapor deposition (MOCVD) technique. The p-type layer with hole concentration of 8.94×1016 cm−3 is composed of nitrogen-doped ZnO using NH3 as the doping source with subsequent annealing in N2O plasma ambient. Silicon-doped GaN film with electron concentration of 1.15×1018 cm−3 is used as the n-type layer. Desirable rectifying behavior is observed from the current–voltage (I–V) curve of the device. The forward turn on voltage is about 4V and the reverse breakdown voltage is more than 7V. A distinct ultraviolet (UV) electroluminescence (EL) with a dominant emission peak centered at 390nm is detected at room temperature from the heterojunction structure under forward bias conditions. The origins of the EL emissions are discussed in comparison with the photoluminescence (PL) spectra. [Copyright &y& Elsevier]

Abstract: ZnO film was firstly prepared by PA-MOCVD method on the substrate pre-coated with GaAs interlayer. Hall measurement found that the GaAs interlayer had important effects on the electrical behavior of the ZnO film. It could make the ZnO film convert to p-type conductivity. The XPS results confirmed that the acceptor was arsenic. And the acceptor level was 130meV above the ZnO valence band maximum. Low-temperature PL measurement was introduced to investigate the optical properties of both as-grown n-type and arsenic doped p-type ZnO films. Then, based on this technology, ZnO homojunction light emitting device (LED) was fabricated with arsenic doped p-type ZnO and unintentionally doped n-type ZnO on GaAs/p+-Si substrate. Its current–voltage (I–V) character showed a typical rectification behavior, which was different from the n-ZnO/p+-Si structure. The UV–visible (385–580nm) electroluminescence was detected under relatively low current injection condition from the n-ZnO/p-ZnO/p+-Si LED. [ABSTRACT FROM AUTHOR]

β gallium oxide (β-Ga 2 O 3) is a promising material for the detection of solar-blind ultraviolet (SBUV). The quality of β-Ga 2 O 3 crystal has a crucial influence on the performance of the photodetectors (PDs). In this paper, SBUV PDs were fabricated on high quality homoepitaxial β-Ga 2 O 3 films grown by metal organic chemical vapor deposition (MOCVD). Both photoconductor PD and Schottky barrier diode (SBD) PD were prepared. The PDs showed excellent performance. For the photoconductor PD, the responsivity and EQE under the illumination of 254 nm light at 20 V bias were respectively 1.08 A/W and 5.32 × 102%. For the SBD PD, the I 254 /I dark at −20 V was 320, and the corresponding rejection ratio I 254 /I 365 was 42. • Solar-blind ultraviolet photodetectors were fabricated on high quality homoepitaxial β-Ga 2 O 3 films grown by MOCVD. • Both photoconductor photodetector and SBD photodetector were fabricated. • The photodetectors showed excellent detection performance. [ABSTRACT FROM AUTHOR]

Abstract: Mg x Zn1− x O thin films were grown on c-sapphire substrates by metal-organic chemical vapor deposition (MOCVD), followed by annealing in vacuum at different temperatures for 1h. The UV emission peak was blue shifted in the photoluminescence (PL) spectra and a dramatic shift of (002) diffraction peak to higher angle was observed in X-ray diffraction (XRD) pattern with increasing anneal temperature. This suggested the band gap and the lattice parameter of Mg x Zn1− x O had been affected by annealing in vacuum. Furthermore, the structure of the film became sparser due to annealing in vacuum. From the X-ray photoelectron spectroscopy (XPS) and ICP of the Mg x Zn1− x O film, we can find that the anneal temperature have an effect on the content of each element in Mg x Zn1− x O quantitatively. In addition, the value of x in Mg x Zn1− x O varied slightly as the annealing temperature increased. The above phenomena indicated that annealing in vacuum could slightly adjust the percentage of Mg indirectly in Mg x Zn1− x O film and offer a good idea in Mg x Zn1− x O devices facture. [Copyright &y& Elsevier]

β gallium oxide (β-Ga 2 O 3) homoepitaxy films were grown on (2 ‾ 01) β-Ga 2 O 3 substrates by metal organic chemical vapor deposition (MOCVD). The effect of growth temperature on the crystalline quality was measured and systematically analyzed. The results showed the growth temperature played an important role in crystalline quality of β-Ga 2 O 3. The optimized single crystalline β-Ga 2 O 3 film was grown at 750 °C, and the full width at half maximum (FWHM) of X-ray diffraction (XRD) rocking curve was 21.6 arcsec, smaller than that of the β-Ga 2 O 3 substrate (26.3 arcsec). The film exhibited a greatly smooth surface and the root-mean-square (RMS) roughness was 0.68 nm. And the arrangement of atoms inside the film was in good accordance with lattice constants of β-Ga 2 O 3. In addition, the effect of the band structure on the luminescent properties of β-Ga 2 O 3 was discussed. • The crystalline quality of the optimized film was superior to that of the substrate. • Atomic arrangement inside the β-Ga 2 O 3 films was displayed. • The effect of band structure on the luminescent properties of β-Ga 2 O 3 was discussed. [ABSTRACT FROM AUTHOR]