High power InGaN/GaN flip-chip LEDs with via-hole-based two-level metallization electrodes

Lv, Jiajiang; Zheng, Chenju; Chen, Quan; Zhou, Shengjun; Liu, Sheng

doi:10.1002/pssa.201600319

Cited by 24 publications

(11 citation statements)

References 48 publications

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“…The LEE of flip-chip LEDs (FCLEDs) was relatively higher compared with the top-emitting LED because of lower refraction index contrast between the sapphire (n = 1.77) and air (n = 1) [34,35]. The FCLEDs can also avoid light absorption by the opaque metal electrodes because light is extracted through sapphire substrate [36,37]. Furthermore, FCLEDs are commonly bonded to a high thermal conductivity submount such as silicon, resulting in a superior heat dissipation capability and a higher light output saturation current density.…”

Section: Introductionmentioning

confidence: 99%

Effect of Dielectric Distributed Bragg Reflector on Electrical and Optical Properties of GaN-Based Flip-Chip Light-Emitting Diodes

Zhou

Liu

et al. 2018

Micromachines

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We demonstrated two types of GaN-based flip-chip light-emitting diodes (FCLEDs) with distributed Bragg reflector (DBR) and without DBR to investigate the effect of dielectric TiO2/SiO2 DBR on optical and electrical characteristics of FCLEDs. The reflector consisting of two single TiO2/SiO2 DBR stacks optimized for different central wavelengths demonstrates a broader reflectance bandwidth and a less dependence of reflectance on the incident angle of light. As a result, the light output power (LOP) of FCLED with DBR shows 25.3% higher than that of FCLED without DBR at 150 mA. However, due to the better heat dissipation of FCLED without DBR, it was found that the light output saturation current shifted from 268 A/cm2 for FCLED with DBR to 296 A/cm2 for FCLED without DBR. We found that the use of via-hole-based n-type contacts can spread injection current uniformly over the entire active emitting region. Our study paves the way for application of DBR and via-hole-based n-type contact in high-efficiency FCLEDs.

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Section: Introductionmentioning

confidence: 99%

Effect of Dielectric Distributed Bragg Reflector on Electrical and Optical Properties of GaN-Based Flip-Chip Light-Emitting Diodes

Zhou

Liu

et al. 2018

Micromachines

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“…To verify usability of the GaN HEMTs on Ammono GaN substrate in microwave designs, a class-AB power amplifier was designed using a small-signal approach based on a very popular Cripps method. This method enables a load impedance optimal for maximum output power level based on DC current-voltage characteristics and small-signal output impedance at a given transistor operating point to be determined [37]. The impedance condition recommended by Cripps suggests a series circuit, as the load, leaving aside the actual structure of transistor output circuit, which in the MESFET (metal semiconductor field effect transistor) and HEMT case has parallel circuit-parallel connection of C DS and R DS on the equivalent circuit ( Figure 7e).…”

Section: Design and Fabrication Of The On Microwave Power Amplifier Umentioning

confidence: 99%

Wide Bandgap Semiconductor Based Micro/Nano Devices

Seo¹

2019

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While conventional group IV or III-V based device technologies have reached their technical limitations (e.g., limited detection wavelength range or low power handling capability), wide bandgap (WBG) semiconductors which have band-gaps greater than 3 eV have gained significant attention in recent years as a key semiconductor material in high-performance optoelectronic and electronic devices [1,2]. These WBG semiconductors have various definitive advantages for optoelectronic and electronic applications due to their large bandgap energy. WBG energy is suitable to absorb or emit ultraviolet (UV) light in optoelectronic devices [3]. It also provides a higher electric breakdown field, which allows electronic devices to possess higher breakdown voltages [4]. In this Special Issue, 13 papers published, including various AlGaN/GaN, SiC, and WO 3 based devices. More than half of papers reported recent progress on AlGaN/GaN high electron mobility transistors (HEMTs) and light emitting diodes (LEDs). Wojtasiak et al., and Sun et al, reported a structural modification of AlGaN/GaN HEMTs to improve turn-on voltage, contact resistance, and on-resistance [5]. Huang et al. investigated high-temperature characteristics of AlGaN/GaN HEMTs and successfully established the thermal model [6]. Mao et al. and Li et al. simulated AlGaN/GaN HEMTs with a large signal model to investigate the kink-effect [7,8]. All of these efforts toward AlGaN/GaN HEMTs enable readers to understand current issues in AlGaN/GaN HEMTs and offer various experimental and theoretical solutions. Beside transistor works, flip-chip GaN LEDs that were combined with TiO 2 /SiO 2 distributed Bragg reflectors (DBRs) was reported by Zhou et al [9]. An improved GaN HEMTs and their microwave performance by employing the asymmetric power-combining was reported by Kim et al [10]. Along with another GaN LED built on a modified micron-size patterned sapphire substrate by Hsu et al. [11]. These GaN LED works are also guided broad readers in the field of optoelectronics and biomedical areas toward future high-performance optogenetics and photonics applications. Also, Sun et al. reported an enhanced AlGaN/GaN Schottky Barrier by engineering the structure of the diode [12]. In addition to AlxGa1-xN system, two SiC simulation efforts have been made by Huang et al. and Jia et al. Huang. They focused on the improvement of higher added efficiency (PAE) factor in 4H-SiC metal semiconductor field effect transistors and breakdown voltage of 4H-SiC diodes, respectively [13,14]. Besides popular AlxGa1-xN and SiC-based applications, three papers report InGaZnO thin-film transistors (TFTs), Si/GaP one-transistor dynamic random-access memory (1T DRAM), and WO 3 thin-film. Zhou et al. investigated a stress tolerance of InGaZnO TFTs with a SiO 2 or Al 2 O 3 passivation layer which shows a stable positive bias during the operation [15]. Kim et al. simulated a novel 1T DRAM design by inserting a GaP pillar which showed a stable high-temperature operation [16]. Finally, Zhang et al. reported th...

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“…In addition, both n-electrode and p-electrode are located on the same side of the flip-chip LED (FCLED) and top-emitting LED (TELED), resulting in severe current crowding around electrodes [12,13,14]. Moreover, the FCLED and TELED suffer from severe heat conducting problems due to the poor thermal conductivity of insulting sapphire substrate [15,16]. Consequently, high junction temperature induced by heat accumulation further impacts the optical and electrical properties of FCLEDs and TELEDs [17,18].…”

Section: Introductionmentioning

confidence: 99%

High-Power GaN-Based Vertical Light-Emitting Diodes on 4-Inch Silicon Substrate

et al. 2019

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We demonstrate high-power GaN-based vertical light-emitting diodes (LEDs) (VLEDs) on a 4-inch silicon substrate and flip-chip LEDs on a sapphire substrate. The GaN-based VLEDs were transferred onto the silicon substrate by using the Au–In eutectic bonding technique in combination with the laser lift-off (LLO) process. The silicon substrate with high thermal conductivity can provide a satisfactory path for heat dissipation of VLEDs. The nitrogen polar n-GaN surface was textured by KOH solution, which not only improved light extract efficiency (LEE) but also broke down Fabry–Pérot interference in VLEDs. As a result, a near Lambertian emission pattern was obtained in a VLED. To improve current spreading, the ring-shaped n-electrode was uniformly distributed over the entire VLED. Our combined numerical and experimental results revealed that the VLED exhibited superior heat dissipation and current spreading performance over a flip-chip LED (FCLED). As a result, under 350 mA injection current, the forward voltage of the VLED was 0.36 V lower than that of the FCLED, while the light output power (LOP) of the VLED was 3.7% higher than that of the FCLED. The LOP of the FCLED saturated at 1280 mA, but the light output saturation did not appear in the VLED.

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High power InGaN/GaN flip-chip LEDs with via-hole-based two-level metallization electrodes

Cited by 24 publications

References 48 publications

Effect of Dielectric Distributed Bragg Reflector on Electrical and Optical Properties of GaN-Based Flip-Chip Light-Emitting Diodes

Effect of Dielectric Distributed Bragg Reflector on Electrical and Optical Properties of GaN-Based Flip-Chip Light-Emitting Diodes

Wide Bandgap Semiconductor Based Micro/Nano Devices

High-Power GaN-Based Vertical Light-Emitting Diodes on 4-Inch Silicon Substrate

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