Systematic Design and Parametric Analysis of GaN Vertical Trench MOS Barrier Schottky Diode With p-GaN Shielding Rings
14 Sep 2021-IEEE Transactions on Electron Devices (Institute of Electrical and Electronics Engineers (IEEE))-Vol. 68, Iss: 11, pp 5707-5713
TL;DR: In this paper, a GaN vertical trench MOS barrier Schottky (TMBS) diodes with embedded p-GaN shielding rings (SRs) were investigated by numerical simulation.
Abstract: We report GaN vertical trench MOS barrier Schottky (TMBS) diodes with embedded p-GaN shielding rings (SRs) and systematically investigate the impact of different structural parameters of the p-GaN SRs on the breakdown performance of the GaN-based vertical TMBS diodes by numerical simulation. The charge coupling effect by the embedded p-n junction at the bottom of the trench homogenize the electric field at the trench corner and alleviate the electric field crowding effect at the Schottky contact region, which can effectively avoid the premature breakdown and improve the reverse blocking capability of the TMBS diodes. The p-GaN SRs can also broaden the overlapped depletion region and shift the pinch-off point into the n−-GaN drift region, thus facilitating the 2-D depletion in the n−-GaN drift layer and boosting the breakdown performance of the conventional TMBS diodes. We found that the doping concentration, thickness, and the width of the p-GaN SRs are closely associated with the electric field distribution and the reverse breakdown characteristics of the GaN-based vertical TMBS diodes. The vertical TMBS diodes with optimal p-GaN SR parameters featured a dramatic improvement in the breakdown voltage from 907 to 1281 V, without an obvious degradation in the ON performance. The proposed TMBS diodes with a p-GaN SR structure can pave the way toward a high-performance GaN vertical power device for high-power and high-efficiency power switch applications.
Citations
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TL;DR: In this article , the reverse and forward characteristics of the gallium nitride (GaN) vertical trench junction barrier Schottky (TJBS) diodes were investigated.
Abstract: We report gallium nitride (GaN) vertical trench junction barrier Schottky (TJBS) diodes and systematically analyzed the effects of the key design parameters on the reverse and forward characteristics of the devices. By taking advantage of the shielding effects from both the trenches and pn junctions in the TJBS structure, the high electric field at the Schottky contact region can be effectively suppressed. We found that the doping concentration, thickness, and spacing of p-GaN, as well as the depth and angle of the trench sidewalls are closely associated with the electric field distribution and the reverse characteristics of the TJBS diodes. With an optimal set of design parameters, the local electric field crowding at either the corner of the trench or the edge of the p-GaN can also be alleviated, resulting in a boosted breakdown voltage of up to 1250 V in the TJBS diodes. In addition, an analytical model was developed to explore the physical mechanism behind the forward conduction behaviors. We believe that the results can provide a systematical design strategy for the development of low-loss, high-voltage, and high-power GaN power diodes towards an efficient power system.
1 citations
TL;DR: In this paper , a GaN-based vertical Schottky barrier diodes (SBDs) with embedded floating islands (FIs) is presented, which can break the theoretical limit of unipolar vertical GaN devices by homogenizing the electric field distribution within the drift layer.
Abstract: We report GaN-based vertical Schottky barrier diodes (SBDs) with embedded floating islands (FIs). The incorporation of FI structure can break the theoretical limit of unipolar vertical GaN devices by homogenizing the electric field distribution within the drift layer. To facilitate comprehensive understanding and structural design of FI SBDs, analytical models for both conducting state and blocking state of GaN FI SBDs are established and verified by TCAD simulation. Parametric optimization for the reverse characteristics of GaN FI SBDs is also carried out systematically. We found that the doping concentration, height of p-GaN FIs, and spacing between adjacent p-GaN FIs are closely associated with the electric field distribution and the reverse breakdown characteristics of vertical FI SBDs. An optimum Baliga’s figure of merit (FOM) of 4.98 GW/cm2 can be achieved, which features a 79.14% enhancement compared with the conventional SBD. The results can provide systematic design guidelines for GaN vertical power electronic systems toward high-voltage, high-speed, and high-power applications.
1 citations
TL;DR: In this paper , a vertical junction barrier Schottky diode with a high-K/low-K compound dielectric structure is proposed and optimized to achieve a high breakdown voltage.
Abstract: A vertical junction barrier Schottky diode with a high-K/low-K compound dielectric structure is proposed and optimized to achieve a high breakdown voltage (BV). There is a discontinuity of the electric field at the interface of high-K and low-K layers due to the different dielectric constants of high-K and low-K dielectric layers. A new electric field peak is introduced in the n-type drift region of junction barrier Schottky diode (JBS), so the distribution of electric field in JBS becomes more uniform. At the same time, the effect of electric-power line concentration at the p–n junction interface is suppressed due to the effects of the high-K dielectric layer and an enhancement of breakdown voltage can be achieved. Numerical simulations demonstrate that GaN JBS with a specific on-resistance (R on,sp) of 2.07 mΩ⋅cm2 and a BV of 4171 V which is 167% higher than the breakdown voltage of the common structure, resulting in a high figure-of-merit (FOM) of 8.6 GW/cm2, and a low turn-on voltage of 0.6 V.
TL;DR: In this article , a vertical junction barrier Schottky diode with a high-K/low-K compound dielectric structure is proposed and optimized to achieve a high breakdown voltage.
Abstract:
A vertical junction barrier Schottky diode with a high-K/low-K compound dielectric structure is proposed and optimized to achieve a high breakdown voltage (BV). There is a discontinuity of the electric field at the interface of high-K and low-K layers due to the different dielectric constants of high-K and low-K dielectric layers. A new electric field peak is introduced in the n-type drift region of junction barrier Schottky diode (JBS), so the distribution of electric field in JBS becomes more uniform. At the same time, the effect of electric-power line concentration at the p-n junction interface is suppressed due to the effects of the high-K dielectric layer and an enhancement of breakdown voltage can be achieved. Numerical simulations demonstrate that GaN JBS with a specific on-resistance (R
on, sp
) of 2.07 mΩ·cm2 and a BV of 4171 V which is 167% higher than the breakdown voltage of the common structure, resulting in a high figure-of-merit (FOM) of 8.6 GW/cm2, and a low turn-on voltage of 0.6 V.
TL;DR: In this paper , a GaN-based vertical SBD was designed to move the peak electric field from the interface of the Schottky junction to the inside of the device at high reverse bias, leading to a higher breakdown voltage and a lower reverse leakage current.
Abstract: In recent years, gallium nitride (GaN) has exhibited tremendous potential for power electronic devices owing to its wider energy band gap, higher breakdown electric field, and higher carrier mobility [1] –[4] . Thanks to the availability of low-dislocation-density bulk GaN substrates and the intrinsic advantages of the vertical device topology, GaN-based vertical SBDs have been developed extensively towards high voltage and high current applications [5] –[7] . However, similar to the lateral GaN SBDs based on the AlGaN/GaN heterostructures, GaN vertical SBDs also suffer from reverse leakage issues due to the energy barrier lowering effect at high reverse bias condition. To achieve a decent device performance, several device architectures have been developed, such as junction barrier Schottky (JBS) diode [8] , MPS diode [9] –[12] , and trench metal-insulator-semiconductor barrier Schottky (TMBS) diode [13] , [14] , which are designed to move the peak electric field from the interface of the Schottky junction to the inside of the device at high reverse bias, leading to a higher breakdown voltage and a lower reverse leakage current.
References
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TL;DR: In this article, the electron transfer into the two-dimensional electron gas (2DEG) of AlGaN/GaN heterojunction field-effect transistors (HFETs) is examined theoretically using a charge-control model.
Abstract: The electron transfer into the two-dimensional electron gas (2DEG) of AlGaN/GaN heterojunction field-effect transistors (HFETs) is examined theoretically using a charge-control model. The model is based on a self-consistent solution of the Poisson, Schrodinger, and charge balance equations, together with the k⋅p Hamiltonian for the valence band states. Realistic surface boundary conditions are imposed, and surface states are included using Fermi–Dirac statistics. Based on the assumption that surface donors are the underlying cause of the 2DEG, a wide range of published data on the 2DEG can be explained. For instance, the variation of the 2DEG density with the AlGaN layer thickness and mole fraction can be accounted for, along with other experimental results, such as the reduction of the 2DEG density when the HFET is capped with a GaN layer, the saturation of the 2DEG density for thick GaN caps, and the increase in the 2DEG density when the surface is passivated.
186 citations
TL;DR: In this article, a GaN-based heterostructure lateral Schottky barrier diodes (SBDs) are investigated on n-SiC substrate, which have very low onset voltage VF = 0.43 V, high reverse blocking VBR >; 1000 V, very low capacitive charge of 0.213 nC/A, and a very fast recovery time of 10 ps.
Abstract: GaN-based heterostructure lateral Schottky barrier diodes (SBDs) grown on n-SiC substrate are investigated in this letter. These SBDs own very low onset voltage VF = 0.43 V, high reverse blocking VBR >; 1000 V, very low capacitive charge of 0.213 nC/A, and a very fast recovery time of 10 ps. These unique qualities are achieved by combining lateral topology, GaN:C back-barrier epitaxial structure, fully recessed Schottky anode (φB = 0.43 eV), and slanted anode field plate in a robust and innovative process. Diode operation at elevated temperature up to 200 °C was also characterized.
151 citations
TL;DR: In this paper, the authors developed a trench MOS-type Schottky barrier diodes (MOSSBDs) for the first time and demonstrated that incorporating the trench structure in Ga2O3 is highly effective for decreasing the reverse leakage current.
Abstract: We developed $\beta $ -Ga2O3 trench MOS-type Schottky barrier diodes (MOSSBDs) for the first time A Si-doped Ga2O3 layer was grown via halide vapor phase epitaxy on a single-crystal Sn-doped $\beta $ -Ga2O3 (001) substrate The trench structure was fabricated using dry etching and photolithography HfO2 film was used as the dielectric film of the trench MOS structure The specific on-resistances ( ${R} _{{ \mathrm{ON},\mathsf {SP}}}$ ) of the normal SBD and trench MOSSBD were about 23 and 29 $\text{m}\Omega $ cm $^{{\mathsf {2}}}$ , respectively The reason the ${R} _{{ \mathrm{ON},\mathsf {SP}}}$ of MOSSBD was a little higher than that of the Schottky barrier diodes (SBD) is that the current path decrease as a result of forming the trench MOS structure The normal SBD had a large reverse leakage current due to the large electric field at the anode metal/semiconductor interface On the other hand, the trench MOSSBD had several orders of magnitude smaller leakage current We, thus, demonstrated that incorporating the trench MOS structure in Ga2O3 is highly effective for decreasing the reverse leakage current
145 citations
TL;DR: In this article, the authors reported vertical GaN-on-GaN p-n diodes with a breakdown voltage (BV) of 1.7 kV and a low differential specific ON-resistance (R_{\mathrm{\scriptscriptstyle ON}}$ of 0.55 with current spreading considered.
Abstract: We report vertical GaN-on-GaN p-n diodes with a breakdown voltage (BV) of 1.7 kV and a low differential specific ON-resistance $R_{\mathrm{\scriptscriptstyle ON}}$ of 0.55 $\text{m}\Omega \cdot \text {cm}^{2}$ with current spreading considered (or 0.4 $\text{m}\Omega \cdot \text {cm}^{2}$ using the diode bottom mesa size), resulting in a figure-of-merit ( $V_{B}^{2}/R_{\mathrm{\scriptscriptstyle ON}})$ of 5.3 GW/cm2 (or 7.2 GW/cm $^{2})$ . These devices exhibit a current swing over 14 orders of magnitude and a low ideality factor of 1.3. Temperature dependent $I$ – $V$ measurements show that the BV increases with increasing temperature, a signature of avalanche breakdown.
143 citations
TL;DR: In this article, the vertical GaN junction barrier Schottky (JBS) rectifiers fabricated with novel ion implantation techniques were shown to achieve specific differential ON-resistances of 1.5-2.5 cm2 and 7-9 cm2, respectively.
Abstract: This letter demonstrates vertical GaN junction barrier Schottky (JBS) rectifiers fabricated with novel ion implantation techniques. We used two different methods to form the lateral p-n grids below the Schottky contact: 1) Mg implantation into n-GaN to form p-wells and 2) Si implantation into p-GaN to form n-wells. Specific differential ON-resistances ( ${R}_{ \mathrm{\scriptscriptstyle ON}}$ ) of 1.5–2.5 $\text{m}\Omega ~\cdot $ cm2 and 7–9 $\text{m}\Omega ~\cdot $ cm2 were obtained in the Mg-implanted and Si-implanted JBS rectifiers, respectively. A breakdown voltage of 500–600 V was achieved in both devices, with a leakage current at high reverse biases at least 100-fold lower than conventional vertical GaN Schottky barrier diodes. The impact of n-well and p-well widths on the ${R}_{ \mathrm{\scriptscriptstyle ON}}$ and BV was investigated. Fast switching capability was also demonstrated. This letter shows the feasibility of forming patterned p-n junctions by novel ion implantation techniques, to enable high-performance vertical GaN power devices.
126 citations