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In this study, we investigate the Ron degradation in D-mode AlGaN/GaN MIS-HEMTs on a Si substrate via an accelerated step stress at different temperatures. We have observed a three-phase Ron degradation behavior, which is highly correlated with a drain bias and back gate bias. First, the Ron degradation increases till a peak value when the drain bias increases. Second, when the drain bias increases...
In this work, we demonstrate a new concept for realizing high threshold voltage (Vth) E-mode GaN power devices with high maximum drain current (ID, max). A gate stack ferroelectric blocking film with charge trap layer, achieved a large positive shift of Vth. The E-mode GaN MIS-HEMTs with high Vth of 6 V shows ID, max 720 mA/mm. The breakdown voltage is above 1100 V.
Wafer sized, high quality continuous films would be a key demand for MoS2 implemented in circuit application. In this study, the growth of few monolayer MoS2 on 4 inches SiO2/Si substrate were demonstrated. The MoS2 thin films were synthesized by sulfurized in a furnace from the ultra-thin MoO3 starting materials by using H2S. The obtained MoS2 thin film examined by Raman analysis and Photoluminescence...
The effect of different buffer layers on the RF losses of GaN-based high-mobility-transistors (HEMTs) on Si substrate has been studied. It is found that the electron inversion layer induced by the residual tensile stress in AlN buffer is responsible for a dominant loss factor. It is first time such mechanisms of the RF loss of GaN/Si is discussed. It is proven that using a thin high-low-high temperature...
In this article, we demonstrate plasma-enhanced atomic layer deposition (PEALD) as an effective passivation technique to establish high interfacial quality of high-k/InGaAs structures. Performing PEALD-AlN as an interfacial passivation layer (IPL), excellent capacitance-voltage (C-V) characteristics have been achieved for the HfO2/n, p-In0.53Ga0.47As MOSCAPs. The effects of AlN-IPL on the effective...
An enhancement-mode AlGaN/GaN MIS-HEMTs with low threshold voltage hysteresis using damage-free neutral beam etched (NBE) gate recess is reported. The NBE can eliminate the plasma-induced defects that generated by irradiating UV/VUV photons as encounted in the conventional inductively coupled plasma-reactive-ion etching (ICP-RIE). Combining the new gate recess process and PEALD-AlN interfacial passivation...
Scalable synthesis of thin tungsten diselenide (WSe2) films on 4-inch silicon substrate with 80 nm silicon dioxide (SiO2) is demonstrated. Cross-sectional transmission electron microscopy (TEM) reveals good control of WSe2 layers. Raman spectroscopy confirms high quality crystal of WSe2 is achieved. Back-gated field-effect transistors (FETs) fabricated on these thin films exhibit p-channel characteristics...
The effect of resistance (Rc) reduction of Ti/Au contact on MoS2 by ICP Ar plasma pretreatment is presented. The lowest Rc of 1.72 ohm-cm was achieved with the ICP treatment condition of 50W (ICP) /2W (chuck) for 10 sec. Compared with the contact without treatment (19.6 ohm-cm), the Rc improves over 10 times, demonstrating the advantage of Ar plasma pre-treatment on MoS2 contact.
We have investigated the effects of surface passivation thickness on the electrical performance of Al-GaN/GaN HEMTs with slant field plates. It is found that the existence of the silicon nitride passivation layer helps to improve the DC characteristics of the devices in terms of the lower drain current collapse, higher maximum DC transconductance, and higher maximum drain current. RF wise, the devices...
Two inches size with high quality layered growth of MoS2 was achieved by PLD on c-plane sapphire substrate. 2∼3 monolayer MoS2 was obtained within 2 inches wafer estimated from Raman analysis and confirmed by cross-sectional view of TEM. Additionally, the oxide states of Mo 3d core level spectra of MoS2, analyzed by XPS, can be effectively reduced by adopting a post sulfurization process in H2S. The...
In situ PEALD processes, including PEALD-AlN pre-gate and post-gate plasma gas treatments, have been studied as a promising passivation method to realize the high interfacial quality of high-k/III-V structures. The formation of excellent dielectric gate stack has been obtained on the HfO2/n, p-In0.53Ga0.47As MOSCAPs by inserting an AlN interfacial layer. The improvements on the electrical properties...
We demonstrate the Au-free GaN HEMT device with the Ti/Al/W Ohmic metal structure. Excellent surface roughness 4.88nm for Ti/Al/W Ohmic stucture was achieved after metallization. The DC characteristics is comparable with conventional HEMTs and the stress performance with high voltage is better than conventional HEMTs.
The electrical properties in the InAlN/AlN/GaN high electron mobility transistor grown by metal-organic vapor deposition (MOCVD) with different growth parameters were investigated in this study. We observed that two-dimensional electron gas (2DEG) channel was influenced by thickness of AlN spacer layer and a stable stage prior to the growth of AlN spacer layer. The TEM images showed the generation...
The epitaxial growth of high quality Ge thin films on different materials of In0.51Ga0.49P and GaAs by ultra high vacuum chemical vapor deposition (UHVCVD) system was studied. The crystallinity of high quality Ge layers on In0.51Ga0.49P and GaAs layers can be proved by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The comparison of surface morphology between Ge grown on In0.51...
A novel AlGaN/GaN/AlGaN double-heterostructure field effect transistor (DH-FET) structure with an inserted LT-AlGaN interlayer grown on 150 mm Si substrate has been studied. The DH-FET structure has been characterized by transmission electron microscopy (TEM), secondary ion mass spectrometry (SIMS) and X-ray diffraction (XRD). It is found that the inserted LT-AlGaN interlayer can further induce the...
The epitaxial growth of GaSb thin film with different V/III ratios on high-lattice-mismatched GaAs (001) substrates by metal organic chemical vapor deposition (MOCVD) was investigated. Under optimal V/III ratio of 2.5, we found that there are many periodic 90° interfacial misfit dislocation (IMF) arrays existing at the GaAs/GaSb interface. The surface roughness is about 3.6nm, 2.2nm, 3.8nm, respectively...
Au-free, fully Cu-metallized InGaP/InGaAs/Ge triple-junction solar cells using Pd/Ge/Cu as front contact and Pt/Ti/Pt/Cu/Cr as back contact were fabricated and the results are reported for the first time. From the specific contact resistance measurement, these Cu-metallized ohmic contacts have low contact resistance in the order of 10−6 Ω-cm2. AES and TEM results clearly show the formation mechanisms...
Wide band gap semiconductor of GaN and its related materials are promising for future power and high frequency applications. In particular, the GaN high electron mobility transistor (HEMT) grown on large-size Si substrate is suitable for low-lost and high power switching applications. The GaN HEMT could be fabricated into convertors and invertors for electrified vehicle (EV). In order to achieve GaN...
InGaP/GaAs dual-junction solar cells with different tunnel diodes (TDs) grown on misoriented GaAs substrates are investigated. It is found that the solar cells with P++-AlGaAs/N++-GaAs TDs grown on 10° off GaAs substrates show a higher external quantum efficiency (EQE) but also generate a higher peak current density (Jpeak) than the solar cells with P++-GaAs/N++-InGaP TDs grown on 10°off GaAs substrates...
The influence of TMAl preflow to the AlN buffer layer and GaN thin film was studied by Optical Microscope, Atomic Force Microscope, X-ray diffraction and Transmission Electron Microscope. Different duration of TMAl preflow lead to substantially differences of the AlN buffer layer and GaN film properties in terms of surface morphology and crystal quality. It was found without TMAl preflow the crystal...
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