The present disclosure relates to a semiconductor light emitting device, comprising: a plurality of semiconductor layers, including a first semiconductor layer having a first conductivity, a second semiconductor layer having a second conductivity different from the first conductivity, and an active layer interposed between the first semiconductor layer and the second semiconductor layer, generating light via electron-hole recombination; a first electrode, supplying either electrons or holes to the plurality of semiconductor layers; a second electrode, supplying, to the plurality of semiconductor layers, electrons if the holes are supplied by the first electrode, or holes if the electrons are supplied by the first electrode; a non-conductive distributed bragg reflector coupled to the plurality of semiconductor layers, reflecting the light from the active layer; and a first light-transmitting film coupled to the distributed bragg reflector from a side opposite to the plurality of semiconductor layers with respect to the non-conductive distributed bragg reflector, with the first light-transmitting film having a refractive index lower than an effective refractive index of the distributed bragg reflector.

Semiconductor Light Emitting Device

There is a great interest in wide-bandgap semiconductor devices and most recently in monolithic GaN structures for power electronics applications. In this paper, vertical p-n diodes fabricated on pseudobulk low defect density ( $10^{4}$ – $10^{6}$ cm $^{-2}$ ) GaN substrates are discussed. Homoepitaxial low-pressure metal organic chemical vapor deposition growth of GaN on its native substrate and being able to control and balance the n-type Si doping with background C impurity has allowed the realization of vertical device architectures with drift layer thicknesses of 6 to 40 $\mu $ m and net carrier electron concentrations of $4\times 10^{15}$ to $2.5\times 10^{16}$ cm $^{-3}$ . This parameter range is suitable for applications requiring breakdown voltages (BVs) of 600 V–4 kV with a proper edge termination strategy. Measured devices demonstrate near power device figure of merit, that is, differential specific on-resistance ( $R_{{{\textrm {sp}}}}$ ) of 2 m $\Omega $ cm $^{2}$ for a BV of 2.6 kV and 2.95 m $\Omega $ cm $^{2}$ for a 3.7-kV device, respectively. The improvement in the substrate quality over the last few years has resulted in the fabrication of diodes with areas as large as 16 mm $^{2}$ , with BVs exceeding 700 V and pulsed (100 $\mu $ s) currents of 400 A. The structures fabricated are utilized to study in detail the temperature dependency of $I$ – $V$ characteristics, impact ionization and avalanche characteristics, and extract (estimate) modeling parameters such as electron mobility in the GaN $c$ -direction (vertical) and hole minority carrier lifetimes. Some insight into device reliability is also provided.

Vertical Power p-n Diodes Based on Bulk GaN

In this paper, we report on 1.2-kV-class vertical GaN-based trench metal–oxide–semiconductor field-effect transistors (MOSFETs) on a free-standing GaN substrate with a low specific on-resistance. A redesigned epitaxial layer structure following our previous work with a regular hexagonal trench gate layout enables us to reduce the specific on-resistance to as low as 1.8 mΩcm2 while obtaining a sufficient blocking voltage for 1.2-kV-class operation. Normally-off operation with a threshold voltage of 3.5 V is also demonstrated. To the best of our knowledge, this is the first report on vertical GaN-based MOSFETs with a specific on-resistance of less than 2 mΩcm2.

http://iopscience.iop.org/article/10.7567/APEX.8.054101/pdf

1.8 mΩ·cm2 vertical GaN-based trench metal–oxide–semiconductor field-effect transistors on a free-standing GaN substrate for 1.2-kV-class operation

Many power switching devices are used in hybrid vehicles (HVs) and electric vehicles (EVs). To improve the efficiency of HVs and EVs, better performance characteristics than those of Si power devices, for example, lower on-resistance, higher speed, higher operation temperature, are required for the power devices. GaN power devices are promising candidates for satisfying the requirements. A lateral GaN power device with a blocking voltage of 600 V and a vertical GaN power device with a blocking voltage of 1200 V are suitable for medium power applications for sub systems and high-power applications for the drive of main motors, respectively. Power device applications in HVs and EVs and the current status of the GaN power device are presented. The reliability of the GaN power device is also discussed.

https://iopscience.iop.org/article/10.7567/JJAP.53.100210/pdf

Recent progress of GaN power devices for automotive applications

In this letter, vertical GaN transistors fabricated on bulk GaN substrates are discussed. A threshold voltage of 0.5 V and saturation current >2.3 A are demonstrated. The measured devices show breakdown voltages of 1.5 kV and specific ON-resistance of 2.2 mΩ-cm
 2
, which translates to a figure-of-merit of V
 BR
 2
/R
 ON
 ~1 × 10
 9
 V
 2
 Ω
 -1
 · cm
 -2
.

1.5-kV and 2.2-m $\Omega $ -cm $^{2}$ Vertical GaN Transistors on Bulk-GaN Substrates

Completely vertical trench gate metal oxide semiconductor field-effect transistors (MOSFETs) have been produced using gallium nitride (GaN) for the first time. These MOSFETs exhibited enhancement-mode operation with a threshold voltage of 3.7 V and an on-resistance of 9.3 mΩcm2. The channel mobility was estimated to be 131 cm2/(Vs) when all the resistances except for that of the channel are considered. Such structures, which satisfy the key words "vertical", "trench gate", and "MOSFET", will enable us to fabricate practical GaN-based power switching devices.

https://iopscience.iop.org/article/10.1143/APEX.1.011105/pdf

Vertical GaN-Based Trench Gate Metal Oxide Semiconductor Field-Effect Transistors on GaN Bulk Substrates

This invention provides a nitride semiconductor light emitting element that, despite the structure that the electrodes are provided opposite to each other and a separation groove for chip isolation or laser lift-off is formed by etching, any damage to a light emitting region does not occur, there is no deterioration, and high brightness can be realized. There is also provided a production process thereof. In an n-type nitride semiconductor layer (2), a level difference (A) is provided in a region over an active layer (3) as viewed from p side. In a part up to this level difference (A), a part of an n-type nitride semiconductor layer (2), an active layer (3), a p-type nitride semiconductor layer (4), the side face of a p electrode (5), and a part of the upper side of the p electrode (5) are covered with a protective insulating film (6). The adoption of a structure comprising a chip side face covered with the protective insulating film (6) is advantageous in that, when a separation groove for chip isolation or laser lift-off is formed by etching, the active layer (3) and the like are not exposed to etching gas for a long period of time.

Nitride semiconductor light emitting element and method for producing nitride semiconductor light emitting element

PROBLEM TO BE SOLVED: To provide a nitride semiconductor light emitting element of high luminance without deterioration, in which electrodes are oppositely installed, separation grooves for chip separation and laser lift-off are formed by etching, and a light emitting region is not damaged, and also to provide a manufacturing method of the light emitting element SOLUTION: In an n-type nitride semiconductor layer 2, a level difference A is formed in a region over an active layer 3 viewed from a p-side A part of the n-type nitride semiconductor layer 2, the active layer 3, a p-type nitride semiconductor layer 4, a part of a side of a p-electrode 5, and an upper side of the p-electrode 5 to a part of the level difference A, are covered by a protection insulating film 6 When the separation grooves for chip separation and laser lift-off are formed by etching, the active layer 3 is not exposed to etching gas for long time by covering a chip side with the protection insulating film 6 COPYRIGHT: (C)2007,JPO&INPIT

Nitride semiconductor light-emitting element and its manufacturing method

This paper focuses on a development and an evaluation of high-speed gate drive circuit for SiC power MOSFET by GaN HEMT. The increasing requests to SiC power devices face to the difficulty of the gate drive because of the mismatching between device parameters and conventional driving circuits for Si power devices. Up to now, high frequency switching is the main target of logic and radio applications of active devices. The drive circuit of power devises has not been considered at the switching over MHz. Moreover, p-type SiC and GaN power devices are still not in our hand in spite of the development of n-type device. Therefore there are difficulties in the design of symmetric circuit structure to avoid the management of ground setting. This paper proposes a gate drive circuit applied GaN devices for high-speed switching of an SiC MOSFET. The proposed circuit is designed for the operation of SiC MOSFET at 10MHz. The feasibility is confirmed through a simple switching circuit.

/pdf/high-speed-gate-drive-circuit-for-sic-mosfet-by-gan-hemt-4xmaihb50e.pdf

High-speed gate drive circuit for SiC MOSFET by GaN HEMT

PROBLEM TO BE SOLVED: To improve external quantum efficiency by forming protrusions and recesses in a translucent conductive layer provided on the surface of a light emitting element composed of a nitride semiconductor, and taking out the light emitted from a light emitting layer effectively with no attenuation by preventing repetition of total reflection on the semiconductor laminate portion in a substrate. SOLUTION: A semiconductor laminate portion 6 is formed on one surface of a substrate 1 by laminating a nitride semiconductor layer including an n-type layer 3 and a p-type layer 5 to form a light emitting layer, and a translucent conductive layer 7 is provided on the surface side of the semiconductor laminate portion 6. A pattern of protrusions and recesses (recess 7a) is formed on the surface of the translucent conductive layer 7. A p-type electrode 8 is provided on the translucent conductive layer 7 and an n-side electrode 9 is provided while being electrically connected with the n-type layer 3 exposed by etching a part of the semiconductor laminate portion 6. COPYRIGHT: (C)2007,JPO&INPIT

Atsushi Yamaguchi

Papers

Vertical GaN-Based Trench Gate Metal Oxide Semiconductor Field-Effect Transistors on GaN Bulk Substrates

Nitride semiconductor light emitting element and method for producing nitride semiconductor light emitting element

Nitride semiconductor light-emitting element and its manufacturing method

High-speed gate drive circuit for SiC MOSFET by GaN HEMT

Semiconductor light emitting element and method of fabricating same