We have investigated the spectral response of front-surface-illuminated GaN and AlGaN/GaN p-i-n ultraviolet photodetectors prepared by reactive molecular beam epitaxy on sapphire substrates. homojunction photodiodes exhibited a peaked near band edge. This enhanced was absent in heterojunction detectors. analyzed effect p-layer thickness diodes magnitude peak photoresponse. The had maximum zero-bias responsivity 0.12 A/W at 364 nm, which decreased more than 3 orders for wavelengths longer 390...

Mg-doped GaN samples prepared by reactive molecular beam epitaxy have been investigated in an attempt to gain insight into the impurity incorporation and origin of auto doping otherwise undoped films. The Hall secondary ion mass spectroscopy data were utilized for analysis possible background impurities such as Si, O, H effort ascertain whether electron concentration is or native defect origin. appear support N vacancy a cause auto-n-type seen GaN. effect ammonia flow rate on Mg atoms films...

A method of growing semi-insulating GaN epilayers by ammonia molecular beam epitaxy through intentional doping with carbon is reported. Thick layers high resistivity are an important element in GaN-based heterostructure field-effect transistors. methane ion source was used as the dopant source. The cracking gas found to be key effective incorporation carbon. High-quality C-doped resistivities greater than 106 Ω cm have been grown reproducibility and reliability. AlGaN/GaN heterostructures on...

The properties of carbon-doped GaN epilayers grown by molecular-beam epitaxy have been studied temperature-dependent resistivity, Hall-effect measurements, x-ray diffraction, and photoluminescence spectroscopy. Carbon doping was found to render the layers highly resistive (>108 Ω cm) quench band edge excitonic emissions. Yellow luminescence is still present in layers. state interpreted as being caused direct compensation carbon acceptors consequently enhanced potential barrier at...

A novel polymer architecture design for GPEs is proposed via in situ copolymerization of VC and a new acylamino-crosslinker. This enables accelerated Li + transport dual-reinforced stable interfaces, contributing to long-lifespan LMBs.

The mechanism of the UV photoenhanced wet etching GaN is determined. does not require an electrical contact to be made sample, and nitrides deposited on insulating substrates (such as sapphire) can etched, unlike photoelectrochemical (PEC) etching. present technique relies adding appropriate oxidizing agent, in this case, peroxydisulfate (S2O82−), KOH solutions. In a similar PEC etching, regions low defect density are preferentially leaving high electron recombination such threading...

High quality GaN epilayers have been grown on oxygen and zinc surfaces of ZnO (0001) substrates by reactive molecular beam epitaxy the effect intermediate buffer layer structural optical properties films has investigated. The characterization were performed using photoluminescence, reflectivity, x-ray double diffraction, atomic force microscopy, transmission electron microscopy. results indicated that was with compressive strain due to difference in thermal expansion coefficient between ZnO....

The growth of high electron mobility GaN on (0001) sapphire by ammonia molecular beam epitaxy is reported. A buffer layer AlN <300 Å initially deposited magnetron sputter epitaxy, a technique where the aluminum source planar dc cathode and used for nitrogen source. epilayer using conventional K cell gallium layers were doped silane. Measured room temperature mobilities 560 cm2/V s observed with carrier densities ∼1.5×1017 cm−3. 4 photoluminescence spectrum showed very strong donor...

Gallium nitride (GaN) thin film samples were grown by ammonia-molecular beam epitaxy. Through room temperature transport measurements, electron mobilities of 560 cm/sup 2//Vs observed for layers with a carrier density 1.5/spl times/10/sup 17/ -3/. Room photoluminescence (PL) spectroscopy revealed the bound exciton transition at 363.0 nm and weak yellow emission whose intensity was sample dependent. At 22 K, main signal sharpened, shifted to 356.9 (3.474 eV), maximum increased factor one...

Self-heating is an important issue for GaN heterostructure field effect transistors (HFETs), especially in high power applications. Here we report the temperature dependence of dc characteristics some HFETs including variation transconductance. We present as a function added power, instead voltage bias, and use data to transform into on average device temperature. For similar devices sapphire SiC, at 20 V VDS 0 VG, increase same ∼2.7 times greater sapphire-based device.

Effects of well thickness and Si doping on the optical properties GaN/AlGaN (MQWs) have been investigated by picosecond time-resolved photoluminescence (PL) measurements. Our results yielded that (i) transitions in nominally undoped MQWs with narrow thicknesses (Lw<40 Å) were blue shifted respect to GaN epilayer due quantum confinement, however, no such shift was evident for larger than 40 Å, (ii) band-to-impurity dominant emission lines large (Lw>40 at low temperatures, (iii)...

AlGaN/GaN double heterostructure channel modulation doped field effect-transistors (DHCMODFETs) with a 1.5–1.75 µm gate length and 3 exhibiting record transconductances saturation current levels have been demonstrated. The maximum normalised drain transconductance are ~1100 mA/mm 270 mS/mm, respectively, at room temperature. Near pinch-off, the breakdown voltage is ~80 V. At an elevated temperature of 300°C, source extrinsic device ~500 120 respectively.

Photoluminescence, Raman, and Hall measurements are reported for Mg doped GaN films grown by molecular beam epitaxy. The compressive tensile stress determined the Raman shift of phonon lines is due to growth conditions rather than presence in film. photoluminescence peak near band-to-band transitions also shifted larger (smaller) energies (tensile) stress. study longitudinal optical A1 branch shows that its line shape affected mostly crystalline quality

We present results on the effect of substrate surface polarity, oxygen and zinc faces, quality GaN epitaxial layers grown ZnO(0001) substrates by reactive ammonia molecular beam epitaxy. The possible effects dealing with disparity in preparation two faces have been eliminated. Photoluminescence reflectivity measurements demonstrate that face leads to higher ZnO compared face. also optical data obtained using different low-temperature AlN, GaN, InxGa1−xN buffer layers. best result has...

Growth of unintentionally doped (UID) semi-insulating GaN on SiC and highly resistive sapphire using the ammonia molecular-beam epitaxy technique is reported. The UID shows room temperature (RT) resistivity 1011 Ω cm well defined activation energy 1.0 eV. balance compensation unintentional donors acceptors such that Fermi level lowered to midgap, controlled by a eV deep defect, which thought be related nitrogen antisite NGa, similar “EL2” center (arsenic antisite) in GaAs. RT range 106–109...

AlGaN/GaN HFETs and silicon MOSFETs have been integrated monolithically on a 〈111〉 substrate. A differential heteroepitaxy technique was used to grow HFET layers substrates while leaving protected areas of atomically smooth in which are built.

An array of microdisks with a diameter about 9 μm and spacing 50 has been fabricated by dry etching from Å/50 Å GaN/AlxGa1-xN (x∼0.07) multiple quantum well (MQW) structure grown reactive molecular beam epitaxy. Optical properties these have studied picosecond time-resolved photoluminescence (PL) spectroscopy. Photoluminescence emission spectra decay dynamics were measured at various temperatures pump intensities. With respect to the original MQWs, we observe strong enhancement transition...

AlGaN/GaN HFET layers were grown by ammonia-MBE on SiC substrates. Fabricated devices showed excellent characteristics: a maximum drain current density >1.25 A/mm, transconductance of 250 mS/mm, fT 103 GHz and fMAX 170 measured for with 0.13 µm gate length. These are the highest ever reported material ammonia-MBE.

We characterize a KOH-based ultraviolet (UV) photoassisted wet etching technique using K2S2O8 as the oxidizing agent. The solution provides well-controlled etch rate and produces smooth high-quality etched surfaces with minimal degradation in surface roughness measured by atomic force microscopy. evolution of pH upon exposure to UV radiation is identified key obtaining controlled rate: Unless steps are taken maintain above 12.0, displays sharp drop that coincides gross roughening surface....

Fabrication of GaN devices presents a number processing issues. Since the AlGaN/GaN material and sapphire substrates are transparent in ultraviolet, light scattering can degrade quality lithography. AlGaN chemically inert materials, highly resistant to wet etching. Schottky contacts fabricated with noble metals (Pt, Au) which present adhesion problems. The approaches solving these difficulties routes fabrication high performance GaN-based modulation doped field effect transistors presented....

Ammonia molecular-beam epitaxy has been used to grow high-quality epilayers of GaN and AlGaN/GaN heterostructure field-effect transistor (HFET) structures on insulating 4H-SiC. The growth process, which a magnetron sputter deposited buffer layer AlN, described previously. Ex situ pretreatment the SiC substrate was found be unnecessary. For single 2.0 μm thick silicon doped epilayer, room temperature (RT) electron mobility 500 cm2/Vs measured at carrier density 6.6×1016 cm−3. HFET structure,...