Review of Recent Progress on Vertical GaN-Based PN Diodes

Zhao

Physica Status Solidi (a)

et al. 2022

The failure analysis of a GaN p–i–n diode is carried out by current–voltage (I–V) tests, emission microscope (EMMI), focused ion beam (FIB), and scanning electron microscope (SEM). A nanotube is found at the location of the luminous spot in the EMMI test. Intentional breakdown experiments show that the breakdown voltages of about 1/3 diodes with the size of are lower than 50 V. These proportions are 1/2 and 5/6 for the diodes with the size of and respectively. At the breakdown injuries of some diodes, the nanotubes are also discovered, which indicates that nanotubes should be one of the important reasons for the reduction of the breakdown threshold voltage.

Section: Introductionmentioning

confidence: 99%

Relationship Between Nanotubes and Breakdown Voltage in GaN p–i–n Diodes

Zhao

Physica Status Solidi (a)

et al. 2022

Crystal Growth & Design

“…Especially, vertical GaN-based devices promise excellent performance at high power density and high operating frequency. 4,5 GaN-based power electronic devices on sapphire and Si and SiC substrates 6−9 suffer from the detrimental effects of large defect densities and strain due to heteroepitaxy. 10,11 Particularly, the treading dislocations (TDs) are the main reason for increased leakage current in vertical devices.…”

Section: ■ Introductionmentioning

confidence: 99%

“…The Baliga's figure of merit 3 of GaN, which describes the fundamental relationship between the basic material properties and the power device performance, is more than twice larger than that of SiC. 4 Thus, GaN-based devices are expected to outperform those based on SiC. Especially, vertical GaN-based devices promise excellent performance at high power density and high operating frequency.…”

Section: ■ Introductionmentioning

confidence: 99%

“…This enables the development of vertical GaN-based devices with outstanding performance. 4,16 Although GaN homoepitaxial growth on HVPE and ammonothermal GaN substrates has been extensively studied, 17−19 critical issues such as thermal decomposition of GaN, 18,20 wavy surface and formation of hillocks and ridges, 21,22 generation of interface and V-shaped dislocations, 23 and impurity incorporation 19 still remain to be solved. One of the main problems in metalorganic chemical vapor deposition (MOCVD) homoepitaxial growth on (0001) GaN substrates is the wavy surface morphology and the presence of macrostep terrace structures.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Recently, GaN substrates fabricated by hydride vapor phase epitaxy (HVPE) and ammonothermal growth have become commercially available at a reasonable price. − The typical TD density in these substrates is in the range of 10 3 to 10 6 cm –2 allowing to reduce the TD densities in homoepitaxial GaN by more than 3 orders of magnitude as compared to heteroepitaxial materials. This enables the development of vertical GaN-based devices with outstanding performance. , …”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Hot-Wall MOCVD for High-Quality Homoepitaxy of GaN: Understanding Nucleation and Design of Growth Strategies

Carrascon

Richter

Nawaz

et al. 2022

Thick GaN layers with a low concentration of defects are the key to enable next-generation vertical power electronic devices. Here, we explore hot-wall metalorganic chemical vapor deposition (MOCVD) for the development of GaN homoepitaxy. We propose a new approach to grow high-quality homoepitaxial GaN in N2-rich carrier gas and at a higher supersaturation as compared to heteroepitaxy. We develop a low-temperature GaN as an optimum nucleation scheme based on the evolution and thermal stability of the GaN surface under different gas compositions and temperatures. Analysis in the framework of nucleation theory of homoepitaxial layers simultaneously grown on GaN templates on SiC and on hydride vapor phase epitaxy GaN substrates is presented. We show that residual strain and screw dislocation densities affect GaN nucleation and subsequent growth leading to distinctively different morphologies of GaN homoepitaxial layers grown on GaN templates and native substrates, respectively. The established comprehensive picture provides a guidance for designing strategies for growth conditions optimization in GaN homoepitaxy. GaN with atomically flat and smooth epilayer surfaces with a root-mean-square roughness value as low as 0.049 nm and low background carbon concentration of 5.3 × 1015 cm–3 has been achieved. It is also shown that there is no generation of additional dislocations during homoepitaxial growth. Thus, our results demonstrate the potential of the hot-wall MOCVD technique to deliver high-quality GaN material for vertical power devices.

Near Zero‐Threshold Voltage P‐N Junction Diodes Based on Super‐Semiconducting Nanostructured Ag/Al Arrays

Wang

et al. 2023

Advanced Materials

energy consumption devices. [1,2] Significantly reducing the energy consumption of semiconductor devices with advanced energy-efficient technologies is highly desirable. Some low resistivity materials, such as graphene, [3,4] carbon nanotube, [5] etc., have shown promise in fabricating semiconductor devices to achieve the energy-saving aim. However, the microstructure, morphology, and size of graphene and carbon nanotubes are hard to control precisely, resulting in unrepeatable and unstable device performance. This is not conducive to the application of these materials for nanodevices.Recently, the discovery of super-semiconductors (SSCs), [6] whose resistivity is 3-10 orders of magnitude lower than conventional semiconductors at room temperature, provides an opportunity to realize ultra-low-power semiconductor devices. The dominant charge carriers in SSCs are hot carriers, including hot electrons and holes, with high energy and mobility. These are formed by absorbing photon energy of thermal infrared via metallic plasmon resonances. [7,8] Different from graphene, whose bandgap is zero, [9][10][11][12] the bandgap of SSCs is approximately equal to the photon energy of thermal infrared, which endows ultra-low-power semiconductor devices with a naturally optimal design. Moreover, better than graphene and carbon nanotubes, SSCs can be fabricated in diversiform periodic patterns with large areas via colloidal lithograph, [13][14][15] which is beneficial to the large-scale manufacturing of nanodevices.Semiconductor p-n junctions are the primary building blocks of many electronic devices, such as transistors, integrated circuits, chips, solar cells, and photodetectors. [16][17][18][19] The power consumption of p-n junction diodes depends on their threshold voltage, [20][21][22] the lower the threshold voltage, the lower the power consumption. In this communication, we report SSC p-n junction diodes (Ag/Al arrays) with a tunable threshold voltage by simply changing the thickness of the bottom Ag film. Most importantly, a near zero-threshold voltage can be achieved with an Ag film of ≈20 nm, which results in ultra-low-power p-n junction diodes: ≈3 W per trillion diodes with a working voltage of 1 V, or ≈30 mW per trillion diodes with an operating voltage of 0.1 V. Furthermore, a built-in electric field in the SSC p-n junction is generated by infrared light photons, resulting in a high breakdown field of ≈1.1 × 10 6 V cm −1 , the same Semiconductor devices are currently one of the most common energy consumption devices. Significantly reducing the energy consumption of semiconductor devices with advanced energy-efficient technologies is highly desirable. The discovery of super-semiconductors (SSCs) based on metallic bi-layer shell arrays provides an opportunity to realize ultra-low-power consumption semiconductor devices. As an example, the achievement of near zero-threshold voltage in p-n junction diodes based on super-semiconducting nanostructured Ag/Al arrays is reported, realizing ultra-low-power p-n junction diodes: ≈...