p-Type Ultrawide-Band-Gap Spinel ZnGa2O4: New Perspectives for Energy Electronics

The family of spinel compounds is a large and important class of multifunctional materials of general formulation AB2X4 with many advanced applications in energy and optoelectronic areas such as fuel cells, batteries, catalysis, photonics, spintronics, and thermoelectricity. In this work, it is demonstrated that the ternary ultrawide-band-gap (∼5 eV) spinel zinc gallate (ZnGa2O4) arguably is the native p-type ternary oxide semiconductor with the largest Eg value (in comparison with the recently discovered binary p-type monoclinic β-Ga2O3 oxide). For nominally undoped ZnGa2O4 the high-temperature Hall effect hole concentration was determined to be as large as p = 2 × 1015 cm–3, while hole mobilities were found to be μh = 7–10 cm2/(V s) (in the 680–850 K temperature range). An acceptor-like small Fermi level was further corroborated by X-ray spectroscopy and by density functional theory calculations. Our findings, as an important step toward p-type doping, opens up further perspectives for ultrawide-band-gap bipolar spinel electronics and further promotes ultrawide-band-gap ternary oxides such as ZnGa2O4 to the forefront of the quest of the next generation of semiconductor materials for more efficient energy optoelectronics and power electronics

Ultra-high critical electric field of 13.2 MV/cm for Zn-doped p-type β-Ga₂O₃

Which the actual critical electrical field of the ultra-wide bandgap semiconductor β-Ga₂O₃ is? Even that it is usual to find in the literature a given value for the critical field of wide and ultra-wide semiconductors such as SiC (3 MV/cm), GaN (3.3 MV/cm), β-Ga₂O₃ (~8 MV/cm) and diamond (10 MV/cm), this value actually depends on intrinsic and extrinsic factors such as the bandgap energy, material residual impurities or introduced dopants. Indeed, it is well known from 1950's that reducing the residual doping (N) of the semiconductor layer increases the breakdown voltage capability of a semiconductor media (e.g. as N by using the Fulop's approximation for an abrupt junction). A key limitation is, therefore, the residual donor/acceptor concentration generally found in these materials. Here, we report that doping with amphoteric Zinc a p-type β-Ga₂O₃ thin films shortens free carrier mean free path (0.37 nm), resulting in the ultra-high critical electrical field of 13.2 MV/cm. Therefore, the critical breakdown field can be, at least, four times larger for the emerging Ga₂O₃ power semiconductor as compared to SiC and GaN. We further explain these wide-reaching experimental facts by using theoretical approaches based on the impact ionization microscopic theory and thermodynamic calculations

Assessment of Large Critical Electric Field in Ultra-wide Bandgap p- type Spinel ZnGa2O4

International audienceThe spinel Zinc Gallate ZnGa2O4 stands out among the emerging ultra-wide bandgap (~5eV) semiconductors as the ternary complex oxide with the widest gap where bipolar conductivity (electrons and holes) has been demonstrated. For power and energy electronic applications, a fundamental property of the material is its critical electric field (Ec), as, for example, the Baliga’s figure of merit scales as ~Ec3 . However, the critical electric field of ZnGa2O4 is yet unknown. In this work, it is carried out with the thermodynamic analysis of point defects and free carriers versus oxygen pressure. According to this analysis, highly resistive p- -type ZnGa2O4 thin films on sapphire and Si substrates were elaborated by metal organic chemical vapor deposition (MOCVD) technique. Hall Effect measurements confirmed a low carrier level at room temperature (estimated at 10 11 cm -3 ), and breakdown voltage characterizations on a polycrystalline thin film on p- -type doped silicon substrates have been performed. We can deduce a value of the critical electric field to be at least 5.3 MV/cm for p- -type ZnGa2O4

Assessment of large critical electric field in ultra-wide bandgap p-type spinel ZnGa2O4

Altres ajuts: the ICN2 is funded also by the CERCA programme / Generalitat de CatalunyaThe spinel zinc gallate ZnGaO stands out among the emerging ultra-wide bandgap (∼5 eV) semiconductors as the ternary complex oxide with the widest gap where bipolar conductivity has been demonstrated. For power and energy electronics, a fundamental property of the material is its critical electric field (E CR) although, for ZnGaO, is yet unknown. In this work, highly resistive p-type ZnGaO thin films on sapphire and Si substrates were grown by metal organic chemical vapor deposition to determine both, the remote acceptor concentration and vertical breakdown voltage. Hall Effect measurements confirmed a low carrier concentration at room temperature of ∼10 cm. From vertical metal-semiconductor-metal structures the average E has been estimated to be of at least 5.3 MV cm, which already is significantly larger than the one of SiC and GaN

Enhancing the intrinsic p-type conductivity of the ultra-wide bandgap Ga2O3 semiconductor

International audienceWhile there are several n-type transparent semiconductor oxides (TSO) for optoelectronic applications (e.g. LEDs, solar cells or display TFTs), their required p-type counterparts oxides are known to be more challenging. For the time being, the n-type TSO with the largest bandgap (~5eV) is Ga2O3 that holds the promisse of extending the light transparency further into the deep ultraviolet. In this work, it is demonstrated that strongly compensated Ga2O3 is also the intrinsic (or native) p-type TSO with the largest bandgap for any reported p-type TSO (e.g. NiO, SnO, delafossites, oxychalcogenides). The achievement of hole mobility in excess of 10 cm 2 /Vs and (high temperature) free hole concentrations in the ~10 17 cm-3 range challenges the current thinking about achieving p-type conductivity in Ga2O3 being "out of question". The results presented in this paper therefore further clarify that p-type Ga2O3 is possible, although more research must be conducted to determine what are the real Ga2O3 prospects for solar blind bipolar optoelectronics and ultrahigh power electronics based in p-n homojunctions

Enhancing the intrinsic p-type conductivity of the ultra-wide bandgap Ga₂O₃ semiconductor

While there are several n-type transparent semiconductor oxides (TSO) for optoelectronic applications (e.g. LEDs, solar cells or display TFTs), their required p-type counterpart oxides are known to be more challenging. At this time, the n-type TSO with the largest bandgap (∼5 eV) is GaO that holds the promise of extending the light transparency further into the deep ultraviolet. In this work, it is demonstrated that strongly compensated GaO is also an intrinsic (or native) p-type TSO with the largest bandgap for any reported p-type TSO (e.g. NiO, SnO, delafossites, oxychalcogenides). The achievement of hole mobility in excess of 10 cm V s and (high temperature) free hole concentrations in the ∼10 cm range challenges the current thinking about achieving p-type conductivity in GaO being "out of the question". The results presented in this paper therefore further clarify that p-type GaO is possible, although more research must be conducted to determine what are the real prospects for GaO solar blind bipolar optoelectronics and ultra-high power electronics based on p-n homojunctions