Negative differential resistance in GaN homojunction tunnel diodes and low voltage loss tunnel contacts

Zhang

IEEE Trans. Electron Devices

et al. 2021

Au nanoparticles (NPs) were drop-casted onto germanium (Ge) devices to investigate the influence of Au NPs on the electronic transport and photodetection properties of Ge metal-semiconductor-metal photodetectors. A significant hysteresis behavior was observed in the current-voltage curves of the Au NP-decorated Ge photodetector, which was ascribed to the energy band bending below the Au NPs and the electrostatic effect of image charges in the Au NPs. More interestingly, at the optical communication wavelength of 1.55 µm, the introduction of Au NPs effectively improved the responsivity of the device from 0.18 to 0.92 A/W. Rather than the localized surface plasmon resonance effect, the increase of responsivity in the Au NP-decorated Ge photodetector was caused by a type-II liked energy band alignment, which enhanced the spatial electron-hole separation effect. These results provide inspiration for the development of novel optoelectronic devices. Index Terms-Au nanoparticles (NPs), electric hysteresis loop, electrostatic effect, germanium (Ge) photodetector, photoresponse enhancement. I. INTRODUCTIONG ERMANIUM (Ge) is one of the most promising materials for near-infrared detection [1], [2], owing to the small bandgap (0.67 eV) and the better compatibility with Si-CMOS processes as compared with III−V and II-VI semiconductor materials. However, the low absorption coefficient of Ge material near 1.55 μm, which is attributed to the direct bandgap of 0.8 eV, is still a major obstacle for its application in optical communication [3], [4].

Section: Resultsmentioning

confidence: 99%

Hysteresis Behavior and Photoresponse Enhancement in Au Nanoparticle-Decorated Ge Photodetectors

Zhang

IEEE Trans. Electron Devices

et al. 2021

Crystal Growth & Design

“…Metal-modulated epitaxy (MME) is a modified form of MBE, which has been described at length elsewhere. , MME enables the enhanced control of surface kinetics to achieve a number of significant results in the III-nitride field, including extreme doping of GaN, − AlGaN, − and AlN. , Furthermore, MME has been used to achieve single-phase InGaN throughout the miscibility gap , and the highest reported In-content InGaN solar cell . Since III-nitrides have extremely high bulk densities and these results were obtained at low growth temperatures (below ∼400 °C for InGaN and below ∼750 °C for AlGaN) where bulk diffusion is limited to a few angstroms, they strongly support our theory of surface-driven phase separation.…”

Section: Introductionmentioning

confidence: 99%

Kinetic Model for Ternary III-Nitride Epitaxy: The Role of Vertical Segregation on Phase Separation

Matthews,

Engel,

Motoki

et al. 2023

Self Cite

Phase separation of indium-bearing III-nitrides is difficult to control and is a major challenge in the development of these materials. On the other hand, this same process does not occur naturally for aluminum gallium nitride but has been leveraged to enable the synthesis of extremely coherent superlattice structures that may lead to interesting applications for AlGaN. This work proposes that phase separation in III-nitride alloys can be attributed to at least four distinct surface-driven mechanisms� thermal decomposition, lateral cation segregation, vertical cation segregation (VCS), and preferential cation incorporation�more than bulk-diffusion-enabled spinodal decomposition. An open source, self-consistent model has been developed to describe the evolution of surface adlayers during the growth of these III-nitride films. This model consists of a system of coupled differential equations which stochastically represent physical mechanisms acting on surface adatoms, and it is used to evaluate the influence of VCS and preferential cation incorporation on self-assembled superlattice formation in AlGaN to both further the understanding of phase separation and test the validity of surface-driven phase separation. Neither preferential incorporation nor VCS alone can explain the experimentally observed composition profiles. However, by combining these two effects, composition profiles similar to those of experimentally grown self-assembled superlattices have been obtained.

“…A recent advancement in the design of III-nitride LEDs is the use of tunnel junction (TJ) contacts. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] A tunnel junction integrated LED replaces the conventional p-GaN contact [28][29][30][31][32] or AlGaN/AlGaN(GaN) contact 33,34) with an inter-band tunnel junction. Tunnel junctions can improve the external quantum efficiency by eliminating the need for lower bandgap contact layers, and by improving hole injection to the p-type layer.…”

mentioning

confidence: 99%

Multi-active region AlGaN UV LEDs with transparent tunnel junctions

Xavier¹,

Ghosh²,

Rahman³

et al. 2023

Appl. Phys. Express

In this work, we demonstrate for the first time two-junction ultraviolet light emitting diodes enabled by transparent tunnel junctions. Low voltage-drop tunnel junctions were realized in Al0.3Ga0.7N layers through a combination of high doping and compositional grading. Capacitance and current-voltage measurements confirmed the operation of two junctions in series. The voltage drop of the two-junction LED was 2.1 times that of an equivalent single-junction LED, and the two-junction LED had higher external quantum efficiency (147%) than the single junction.