GaN Semiconductor Research Articles

Effect of Metal Contacts on a GaN/Sapphire-Based MSM Ultraviolet Photodetector

We report the fabrication of a GaN/sapphire ultraviolet (UV) photodetector (PD) with asymmetric (Pt-Ag) and symmetric (Pt-Pt) metal–semiconductor–metal (MSM) structure. The fabricated devices display Schottky behavior. Time-dependent photoresponse analysis reveals a significant enhancement in photocurrent leading to a photoresponsivity of 37 mA/W and 267 mA/W under 13 mW optical power at 5 V bias for Pt-Pt and Pt-Ag devices, respectively. Further, power-dependent measurements reveal a peak responsivity of 633 mA/W at 4mW optical power and 5 V bias for the Pt-Ag asymmetric MSM photodetector. The significant enhancement in responsivity for asymmetric MSM UV PD is ascribed to the built-in potential gradient in the GaN semiconductor, which drives a large number of charge carriers for enhanced charge collection. Further, the noise equivalent power was lowest for the Pt-Ag MSM structure, which was calculated to be 4.6 × 10−14 WHz−1/2. This high performance asymmetric MSM GaN UV PD can be integrated into efficient UV PD-based applications.

Epitaxial growth of perovskite (111) 0.65PMN-0.35PT films directly on wurtzite GaN (0002) surface

PMN-PT films were deposited on GaN/sapphire substrates via pulsed laser deposition without any intermediate buffer layers, and epitaxial perovskite (111) 0.65PMN-0.35PT films on wurtzite GaN(0002) surfaces were obtained by adjusting the experimental parameters including substrates temperature and O $$_2$$ pressure. The microstructures and electrical properties of PMN-PT/GaN heterostructure were characterized by reflection high-energy electron diffraction, X-ray diffraction, atom force microscope, transmission electron microscope and polarization–electric field (P–E) measurements. The as-grown PMN-PT films exhibit highly (111) oriented perovskite crystal structure. The in-plane orientation relationship of PMN-PT film with respect to GaN is (111) $$\times$$ [11-2] PMN-PT//(0002) $$\times$$ [11-20] GaN. A domain matching epitaxy model is proposed to account for the epitaxial growth mechanism of PMN-PT on GaN. The P–E curves show typical ferroelectric characteristics, while the remnant polarization and coercive field are about 18.1 $$\upmu$$ C/cm $$^2$$ and 75 kV/cm, respectively. This work provides a good start point for the further development of advanced electronic devices based on the integration of ferroelectric PMN-PT with wide-gap GaN semiconductor.

52‐3: Invited Paper: Combining Engineered EPI Growth Substrate Materials with Novel Test and Mass‐Transfer Equipment to Enable MicroLED Mass‐Production

Advances in layer‐transfer methods are making large‐area growth templates a reality for GaN and GaAs compound semiconductors. QMAT will introduce its layer‐transfer technology tuned for microLED applications integrating functional layers that simplify printability and testability. MicroLED yield and test challenges will also be discussed.

GaN-based single-chip frontend for next-generation X-band AESA systems

AbstractA next generation of active electronically scanned array (AESA) antennas will be challenged with the need for lower size, weight, power, and cost. This leads to enhanced demands especially with regard to the integration density of the radio frequency-part inside aT/Rmodule. The semiconductor material GaN has proven its capacity for high-power amplifiers (HPA), robust receive components as well as switch components for separation of transmit and receive mode. This paper will describe the design and measurement results of a GaN-based single-chipT/Rmodule frontend (HPA, low noise anplifier, and single-pole double-throw (SPDT)) using UMS GH25 technology and covering the frequency range from 8 GHz to 12 GHz. The key performance parameters of the frontend are 13 W minimum transmit (TX) output power over the whole frequency range with peak power up to 17 W. The frontend in receive (RX) mode has a noise figure below 3.2 dB over the whole frequency range, and can survive more than 5 W input power. The large signal insertion loss of the used SPDT is below 0.9 dB at 43 dBm input power level.

9.1: Invited Paper: Materials, Process and Production Equipment Considerations to Achieve High‐Yield MicroLED Mass‐Production

Advances in layer‐transfer methods are making large‐area growth templates a reality for GaN and GaAs compound semiconductors. QMAT will introduce its layer‐transfer technology tuned for microLED applications integrating functional layers that simplify printability and testability. MicroLED yield and test challenges will also be discussed.

Defect Characterization, Imaging, and Control in Wide-Bandgap Semiconductors and Devices

Wide-bandgap semiconductors are now leading the way to new physical phenomena and device applications at nanoscale dimensions. The impact of defects on the electronic properties of these materials increases as their size decreases, motivating new techniques to characterize and begin to control these electronic states. Leading these advances have been the semiconductors ZnO, GaN, and related materials. This paper highlights the importance of native point defects in these semiconductors and describes how a complement of spatially localized surface science and spectroscopy techniques in three dimensions can characterize, image, and begin to control these electronic states at the nanoscale. A combination of characterization techniques including depth-resolved cathodoluminescence spectroscopy, surface photovoltage spectroscopy, and hyperspectral imaging can describe the nature and distribution of defects at interfaces at both bulk and nanoscale surfaces, their metal interfaces, and inside nanostructures themselves. These features as well as temperature and mechanical strain inside wide-bandgap device structures at the nanoscale can be measured even while these devices are operating. These advanced capabilities enable several new directions for describing defects at the nanoscale, showing how they contribute to device degradation, and guiding growth processes to control them.

Characterization of quaternary Zn/Sn-codoped GaN films obtained with Zn x Sn0.04GaN targets at different Zn contents by the RF reactive magnetron sputtering technology

Quarternary (Zn, Sn, Ga)N thin films with co-existing a large amount of acceptor and donor were purposely fabricated in order to heavily distort the GaN lattice and to extend the degenerated GaN semiconductor to a different aspect. The ZnSnGaN films were made of reactive sputtering with single cermet targets containing Zn, Sn, Ga, and GaN under the nitridation atmosphere. By varying the Zn content at fixed 4% Sn content, different Zn x Sn0.04Ga0.96−xN targets at x = 0, 0.03, 0.06, and 0.09 were prepared for Zn/Sn-x-GaN films. With increasing the Zn content, Zn/Sn-x-GaN due to the charge compensation changed from semiconducting n type to p type, and from high electron concentration of 4.1 × 1017 cm−3 to high hole concentration of 3.3 × 1017 cm−3. The optical band gap changed from 3.12 to 2.89 eV, related to the formation in ZnGa acceptor and SnGa donor defects. The hetero- and homo-junction diodes were fabricated. The n-Zn0.03Sn0.04GaN/p-Zn0.09Sn0.04GaN homo-junction diode tested at 25 °C had the turn-on voltage of 0.9 V, leakage current density of 6.0×10−5 A/cm2 at − 1 V, breakdown voltage of 4.7 V, current density of 2.4 × 10−2 A/cm2 at 5 V, ideality factor of 3.4, and barrier height of 0.65 eV.

Self-injection locked blue laser

We demonstrate a 446.5 nm GaN semiconductor laser with sub-MHz linewidth. The linewidth reduction is achieved by locking the laser to a magnesium fluoride whispering gallery mode resonator characterized with 109 quality factor. Self-injection locking ensures single longitudinal mode operation of the laser.

InN/GaN quantum dot superlattices: Charge-carrier states and surface electronic structure

We have theoretically investigated the electron energy spectra and surface states energy in the three dimensionally ordered quantum dot superlattices (QDSLs) made of InN and GaN semiconductors. The QDSL is assumed in this model to be a matrix of GaN containing cubic dots of InN of the same size and uniformly distributed. For the miniband’s structure calculation, the resolution of the effective mass Schrödinger equation is done by decoupling it in the three directions within the framework of Kronig–Penney model. We found that the electrons minibands in infinite ODSLs are clearly different from those in the conventional quantum-well superlattices. The electrons localization and charge-carrier states are very dependent on the quasicrystallographic directions, the size and the shape of the dots which play a role of the artificial atoms in such QD supracrystal. The energy spectrum of the electron states localized at the surface of InN/GaN QDSL is represented by Kronig–Penney like-model, calculated via direct matching procedure. The calculation results show that the substrate breaks symmetrical shape of QDSL on which some localized electronic surface states can be produced in minigap regions. Furthermore, we have noticed that the surface states degeneracy is achieved in like very thin bands located in the minigaps, identified by different quantum numbers n[Formula: see text], n[Formula: see text], n[Formula: see text]. Moreover, the surface energy bands split due to the reduction of the symmetry of the QDSL in z-direction.

The tuning effect of the electric field on the physical properties of some typical wurtzite semiconductors

Under the tuning of an external electric field, the variation of the geometric structures and the band gaps of the wurtzite semiconductors ZnS, ZnO, BeO, AlN, SiC and GaN have been investigated by the first-principles method based on density functional theory. The stability, density of states, band structures and the charge distribution have been analyzed under the electric field along (001) and (00[Formula: see text]) directions. Furthermore, the corresponding results have been compared without the electric field. According to our calculation, we find that the magnitude and the direction of the electric field have a great influence on the electronic structures of the wurtzite materials we mentioned above, which induce a phase transition from semiconductor to metal under a certain electric field. Therefore, we can regulate their physical properties of this type of semiconductor materials by tuning the magnitude and the direction of the electric field.

Flexible Modulation of Electronic Band Structures of Wide Band Gap GaN Semiconductors Using Bioinspired, Nonbiological Helical Peptides

AbstractModulation of the electronic band profiles of wide band gap GaN semiconductors is achieved by the macromolecular dipole potentials exerted from ordered monolayers of synthetic, nonbiological aldehyde terminated helical peptides deposited on wet chemically oxidized GaN surfaces functionalized with aminosilanes. The selective coupling of either N‐ or C‐terminal to the amino‐terminated surface enables one to control the direction of the dipole moment, while the number of amino acids determines its magnitude. After confirming the formation of highly ordered peptide monolayers, the impact of macromolecular dipole potentials is quantified by electrochemical impedance spectroscopy. Moreover, the chronoamperometry measurements of ferrocene‐terminated peptides suggest that the transfer of electrons injected from ferrocene follows inelastic hopping, while the current responses of peptides with no ferrocene moieties are purely capacitive. Finally, the same functionalization steps are transferred to GaN/AlGaN/GaN high electron mobility transistor structures. Stable and quantitative modulation of the current–voltage characteristics of the 2D electron gas by the deposition of bioinspired peptides is a promising strategy for the macromolecular dipole engineering of GaN semiconductors.

1S-A1-2Innovate Electron Beam by GaN Semiconductor Photocathodes Conducive to Single Shot Imaging

1S-A1-2Innovate Electron Beam by GaN Semiconductor Photocathodes Conducive to Single Shot Imaging

High work function MoO2 and ReO2 contacts for p-type Si and GaN by a room-temperature non-vacuum process

High work function molybdenum (Mo) and rhenium (Re) di-oxides were studied without vacuum and thermal process to investigate the contact properties on p-type Si and GaN semiconductors. Polyvinyl alcohol (5wt% PVA) was used as a binder for the metal oxide powder. ReO2 showed lower electrical resistivity < 0.023 ± 0.004Ωcm and better contact characteristics compared to MoO2. Ohmic contacts were formed easily on p-type Si (ρ = 9.77Ωcm) using ReO2 and MoO2. The metal oxide/semiconductor Schottky diodes fabricated by forming contacts on n-type Si (ρ = 2.44Ωcm) were investigated by comparing diode parameters indicating different contact barrier properties of metal oxides. As a wide energy bandgap semiconductor, p-type GaN was utilized to investigate metal oxide contact properties on a high work function semiconductor. Ohmic contact on p-type GaN was obtained using ReO2 after the surface treatment by boiling aqua regia.

Controlling charges distribution at the surface of a single GaN nanowire by in-situ strain

Effect of the strain on the charge distribution at the surface of a GaN semiconductor nanowire (NW) has been investigated inside transmission electron microscope (TEM) by in-situ off-axis electron holography. The outer and inner surfaces of the NW bent axially under compression of two Au electrodes were differently strained, resulting in difference of their Fermi levels. Consequently, the free electrons flow from the high Fermi level to the low level until the two Fermi levels aligned in a line. The potential distributions induced by charge redistribution in the two vacuum sides of the bent NW were examined respectively, and the opposite nature of the bounded charges on the outer and inner surfaces of the bent NW was identified. The results provide experimental evidence that the charge distribution at the surfaces of a single GaN NW can be controlled by different strains created along the NW.

Uma avaliação dos potencias LDA, GGA-PBEsol, BJ, mBJ original, mBJ P-presente e mBJ P-semicondutor em cálculos dos band gaps dos semicondutores: ZnO, GaN, TiO2 e SnO2 utilizando a teoria funcional da densidade

Este trabalho apresenta uma avaliação dos potenciais LDA, GGA-PBEsol, BJ, mBJ original, mBJ P-presente e mBJ P-semicondutor em cálculos dos band gaps dos semicondutores ZnO, GaN, TiO2 e SnO2 utilizando o formalismo da Teoria Funcional da Densidade (DFT). O objetivo de utilizar diferentes potenciais é avaliar qual destes descreve em acordo com o experimental tanto os valores quanto a natureza dos band gaps dos semicondutores. Nos cálculos das estruturas eletrônicas (estrutura de bandas), estes potenciais descreveram em pleno acordo com os experimentais a natureza direta → dos band gaps destes compostos. No entanto, o potencial mBJ P-semicondutor foi o único que descreveu em concordância com o experimental os valores dos gaps. Os valores calculados dos gaps com o potencial mBJ P-semicondutores foram de 3,37 eV (ZnO), 3,48 eV (GaN), 3,06 eV (TiO2) e 3,80 eV (SnO2), os quais concordam com valores experimentais.

Propagation and interaction of two soliton in a quantum semiconductor plasma with exchange correlation effects

Collisions of solitary pulses in a four species quantum semiconductor plasma consisting of degenerate electrons, degenerate holes, and non-degenerate ions are investigated. The electron and hole exchange-correlation forces between the identical particles when their wave functions overlap due to the high number densities are considered. Using the extended Poincarê–Lighthill-Kue method in opposite directions, two Korteweg-de Vries equations are derived. Hirota's method is used to derive the analytical phase shifts after the collision of one soliton and two soliton. Typical values for GaAs, GaSb, GaN, and InP semiconductors are considered to analyze the effects after collisions.

Perspective of Loss Mechanisms for Silicon and Wide Band-Gap Power Devices

With the commercial availability of GaN and SiCbased power semiconductor devices having significantly improved material characteristics, there is a need to discuss the perspective of the underlying physical loss mechanisms of these devices versus their silicon counterparts. This article will compare latest generation Superjunction power transistors versus e-mode GaN HEMTs and SiC MOSFETs in terms of semiconductor losses and their potential for further improvement. A short application section will give practical information on best matching circuits for each device concept.

State-of-the-Art and Prospective for Mass-Production of Wide Band Gap Semiconductor Crystals ZnO and GaN by Solvothermal Technology( Basic Concept Enables Breakthrough)

State-of-the-Art and Prospective for Mass-Production of Wide Band Gap Semiconductor Crystals ZnO and GaN by Solvothermal Technology( Basic Concept Enables Breakthrough)

Magnetism induced by Ga vacancy in rare earth R(R=Gd,Eu,Tm)doped GaN

In recent years, GaN doped with rare earth has attracted much attention due to its potential application in spintronic devices and optoelectronic devices. Based on the density functional theory, we investigate the magnetic moment, formation energy, and electronic structure in R (R= Gd, Eu, Tm) doped GaN semiconductors. We focus on the contribution of Ga vacancy to the magnetism, and calculate the formation energy of different Ga vacancies in the presence of Gd, Eu, or Tm dopants, and that of Gd, Eu, Tm dopants in native defects of Ga vacancy. The possible stable defect structures in GaN are given according to their formation energy. It is found that the Ga vacancies prefer to form cluster, and the formation energy of concentrated Ga vacancies is low compared to separated Ga vacancies. The 5d electrons of rare earth as well as 4f electrons have a larger contribution to the magnetism of GaN:R with Ga vacancy than without Ga vacancy. In addition, intermediate bands were observed in GaN:R with intrinsic defects, which possibly opens the potential application of R-doped semiconductors in the third generation high efficiency photovoltaic devices.

Efficient temperature sensing using photoluminescence of Er/Yb implanted GaN thin films

The luminescence characteristics of GaN films implanted with Er at low doses were evaluated. The defect-related yellow luminescence (YL) and green luminescence (GL) bands observed under direct excitation with 488nm were attributed to the transitions via different charge levels of the same defect. The quenching behavior of the luminescence intensity either with the temperature or concentration variation can be attributed to nonradiative energy transfer (ET) and/or charge transfer by trapping impurities. The temperature dependence of the YL band allowed us to identify the defect responsible for this emission. The best candidate for this defect was found to be a nitrogen-vacancy. A GaN sample co-doped with Er3+ and Yb3+ ions was prepared, and its optical properties were analyzed. The incorporation of Yb3+ improved the PL emission intensity in the visible region. This feature results from the efficient ET processes between these two doping ions. The color coordinate analysis indicates that Er3+/Yb3+ co-doped GaN semiconductor emits light with color in the white-light region. To investigate the temperature sensing application of the synthesized co-doped semiconductor, the temperature-sensing performance was evaluated using the fluorescence intensity ratio technique in the temperature range 200–300K. The significant temperature sensitivity indicates its potential as a temperature sensing probe. The maximum sensitivity was 15×10−4K−1 at 200K.