Epitaxial Growth of ZnGa₂O₄: A New, Deep Ultraviolet Semiconductor Candidate

Abstract

ZnGaO films were grown on c-plane sapphire substrates by metal organic chemical vapor deposition using diethylzinc (DEZn), triethylgallium (TEGa), and oxygen. The flow rate of DEZn was 10–60 sccm, and those of TEGa and oxygen were held constant. The ZnGaO film prepared at a DEZn flow rate of 10 sccm adopted a (2̅01)-oriented single-crystalline β-Ga2O3 phase, whereas those prepared at 30–60 sccm exhibited a (111)-oriented single-crystalline ZnGa2O4 phase. On the basis of Hall measurements, ZnGaO films (10 sccm DEZn) possessed very poor electrical properties, which were similar to those of β-Ga2O3. On the other hand, the carrier concentration in ZnGaO films increased from 1.94 × 1014 to 6.72 × 1016 cm–3, and the resistivity decreased from 5730 to 67.9 Ω-cm when increasing the DEZn flow rate from 30 to 60 sccm. According to compositional analyses, the improved electrical properties of ZnGaO films upon increasing DEZn flow rate from 30 to 40 sccm are due to the increasing Zn content, and the enhancement from 50 to 60 sccm could be due to increased C content. Cathodoluminescence results also confirm the ZnGa2O4 structure for ZnGaO films prepared at DEZn flow rates of 30–60 sccm and reveal their use for ultraviolet applications.

Deep-Ultraviolet Photodetectors Based on Epitaxial ZnGa2O4 Thin Films

“…Post-annealing affected the crystalline quality, surface properties, altered defects, and electrical properties of ZnGa 2 O 4 films. Our previous studies have demonstrated the quality of as-grown ZnGa 2 O 4 films, which contain lower degree of crystallinity and higher point defects than those of annealed ZnGa 2 O 4 films 11 . The dark current of as-grown ZnGa 2 O 4 film PDs (Idark ~1 mA at a 20 V bias) was approximately 10 8 times higher than that of annealed PDs based on ZnGa 2 O 4 films so that the photocurrent stimulated by DUV light was difficult to distinguish.…”

“…The flow rates of DEZn, TEGa, and oxygen were maintained at 40, 50, and 200 sccm, respectively. Previously, we have systematically investigated in details the effects of different growth parameters on the successfully grown (111)-oriented single-crystalline ZnGa 2 O 4 films by MOCVD technique 11 . The as-grown epilayer was subsequently annealed in the furnace for 1 h at 700, 800 and 900 °C in nitrogen ambient.…”

“…These films have been fabricated to metal–oxide–semiconductor field-effect transistors 10 . The correlations among crystal, microstructural, morphological, compositional, CL, and electrical properties of these ZnGa 2 O 4 films were also analyzed in details in our previous study 11 . The calculated carrier concentration, mobility, and resistivity of the ZnGa 2 O 4 films were 6.72 × 10 16  cm −3 , 1.4 cm 2 /Vs, and 67.9 Ω-cm, respectively.…”

Influence of Annealing Temperature on the Properties of ZnGa2O4 Thin Films by Magnetron Sputtering

“…ZnGa 2 O 4 materials have recently gained increased attention [2,3]. These materials are widely applied in vacuum fluorescent and field emission displays, gas sensors, electronic devices, and solar-blind ultraviolet photodetectors (PDs) due to their high transparency in the deep ultraviolet (DUV) spectral region, excellent thermal and chemical stability, and wide optical band gap (~5 eV) [4][5][6].…”

Structural Characteristics and Photoluminescence Properties of Sputter-Deposition ZnGa2O4 Thin Films on Sapphire and Si(100) Substrates

“…ZnGa 2 O 4 phosphor materials have been prepared by several methods, including radio-frequency (RF) magnetron sputtering [6], sol-gel processing [7], metal organic chemical vapor deposition (MOCVD) [8] and pulsed laser deposition [9]. However, they are mostly used to conduct synthesis of one-dimensional nanostructures (nanoparticles, nanowires and nanotubes) and are known to improve the emission characteristics of ZnGa 2 O 4 phosphor powder [10][11][12].…”