Low-pressure Metallorganic Chemical Vapor Deposition Research Articles

DC characteristics of lattice-matched InAlN/AlN/GaN high electron mobility transistors

Lattice-matched InAlN/AlN/GaN high electron mobility transistors (HEMTs) grown on sapphire substrate by using low-pressure metallorganic chemical vapor deposition were prepared, and the comprehensive DC characteristics were implemented by Keithley 4200 Semiconductor Characterization System. The experimental results indicated that a maximum drain current over 400 mA/mm and a peak external transconductance of 215 mS/mm can be achieved in the initial HEMTs. However, after the devices endured a 10-h thermal aging in furnace under nitrogen condition at 300 °C, the maximum reduction of saturation drain current and external transconductance at high gate-source voltage and drain-source voltage were 30% and 35%, respectively. Additionally, an increased drain-source leakage current was observed at three-terminal off-state. It was inferred that the degradation was mainly related to electron-trapping defects in the InAlN barrier layer.

Enhancing the Emission Efficiency of In0.2Ga0.8N ∕ GaN MQW Blue LED by Using Appropriately Misoriented Sapphire Substrates

In this paper, we report the fabrication of an multiple-quantum-well (MQW) structure on vicinal sapphire substrates with a very small offset angle of 0–1° by low-pressure metallorganic chemical vapor deposition. Our study demonstrates that the quality of the MQW structure is very sensitive to the offset angle of the vicinal substrate. High-resolution X-ray diffraction analyses demonstrated high-order satellite peaks and clear fringes between them for all MQW structures fabricated, from which the interface roughness (IRN) was estimated. The IRN of the MQW structure fabricated on 0.2° off sapphire substrate was determined as 1.36% of the quantum well layer period. Besides, reciprocal lattice mapping was employed to examine the strain status of the MQW. The lattice relaxation of the same specimen mentioned above was estimated to be . It is therefore manifested that an MQW structure with abrupt interfaces and good layer periodicity was grown. From it, a shortest radiative lifetime of and a lowest fluctuation of in the emission energy of micro-photoluminescence mapping were achieved. In addition, superior material qualities of the whole film fabricated on 0.2° off substrate were recognized by cross-sectional transmission electron microscopy. Based on the results mentioned above, a high-quality MQW blue light, emitting diode (LED) has been fabricated on 0.2° off substrate, which demonstrated a strong room-temperature electroluminescence emission at the wavelength of and with the full width at half maximum of only . The same device also showed an output power of and an external quantum efficiency of 19.2%. Both these characteristics are improved drastically compared with the devices fabricated on the substrates with other offset angles. Conclusively, the use of an appropriately misoriented sapphire substrate is suggested to be effective for elevating the emission efficiency of MQW blue LED fabricated thereon.

Low-Pressure Metallorganic Chemical Vapor Deposition of Fe2O3 Thin Films on Si(100) Using n-Butylferrocene and Oxygen

thin films have been deposited on Si(100) substrates using n-butylferrocene and oxygen in a low-pressure metallorganic chemical vapor deposition reactor. The iron precursor is liquid at room temperature having a high enough vapor pressure; its thermogravimetric analysis shows that it undergoes clean evaporation without decomposition. The growth rates were studied in the temperature range of . The resulting thin films were characterized for structure and morphology using X-ray diffraction and scanning electron microscopy. Their composition was analyzed using energy-dispersive X-ray spectroscopy, and chemical bonding states were probed using X-ray photoelectron spectroscopy. Films deposited at were mostly noncrystalline and had carbon contamination. Films deposited at higher temperatures were crystalline .

Structural and Optical Properties of Nanocrystalline Er2O3 Thin Films Deposited by a Versatile Low-Pressure MOCVD Approach

Nanocrystalline thin films have been grown on Si(100) by low-pressure metallorganic chemical vapor deposition in the temperature range of using the tris(isopropylcyclopentadienyl)erbium precursor and . The growth kinetics has been investigated in real time using laser reflectance interferometry as a function of growth parameters, and three different steps have been highlighted: (i) the incubation, (ii) the nucleation, and (iii) the growth stages. It is demonstrated that functionalization of the Si substrate surface is important for shortening the incubation time and, consequently, reducing subcutaneous oxidation of the Si substrate and for preventing nonhomogeneous nucleation that yields rough films. The growth kinetics has been correlated with film properties. X-ray diffraction patterns show strongly (111) oriented thin films even at temperature as low as ; however, a deposition temperature of is optimal for obtaining films with highest refractive index and lowest surface roughness (. Transmission electron microscopy shows very sharp interfaces and compact films. Spectroscopic ellipsometry analysis of the optical properties shows a very high refractive index comparable to that of single crystal and a very high transparency in the visible–ultraviolet energy photon range.

Comparative Studies on Double δ -Doped Al0.3Ga0.7As ∕ InxGa1 − xAs ∕ GaAs Symmetrically Graded Doped-Channel Field-Effect Transistors

This work provides comparative studies of a double δ-doped symmetrically graded doped-channel field-effect transistor (DD-DCFET) with respect to a conventional double δ-doped pseudomorphic high electron mobility transistor (pHEMT) and a conventional DCFET structure. All threes samples, grown by the low-pressure metallorganic chemical vapor deposition (LP-MOCVD) system, have identical layer structures except for their different doping schemes. Comprehensive investigations on the static, microwave, and temperature-dependent characteristics have been made. Possessing the advantages of DCFETs and pHEMTs, the proposed DD-DCFET has demonstrated comprehensively superior linearity, current drive, voltage gain, high-frequency characteristics, and thermal stability characteristics. It is promisingly suitable for millimeter-wave integrated circuit applications.

Comparison of Al0.32Ga0.68N ∕ GaN Heterostructure Field-Effect Transistors with Different Channel Thicknesses

heterostructure field-effect transistors (HFETs) grown by low-pressure metallorganic chemical vapor deposition are successfully fabricated. A Mg-doped insulating layer is inserted to suppress the leakage current, improve the breakdown voltages, and yield excellent pinch-off characteristics. Moreover, HFETs with different channel thicknesses of 1200, 1500, and are investigated. Experimental results show that an HFET with a thick channel layer has the highest electron mobility, electron concentration, drain current, and extrinsic transconductance.

Improved Nucleation Behavior of Ru Thin Films Prepared by MOCVD on TiCl[sub 4] Pretreated Substrates

Ru films were deposited on SiO 2 and TiN substrates by low-pressure metallorganic chemical vapor deposition (MOCVD). To improve the low nucleation density of Ru on the two types of substrates and the resultant rough surface morphologies of the deposited films, the surface was pretreated with TiCl 4 molecules using a repeated cyclic pulse and purge process. In this way, the nucleation density of Ru on the pretreated substrates was increased and continuous and smoother Ru films were obtained. X-ray photoelectron spectroscopy revealed that the improvement of the nucleation property is related to the change in the binding characteristics of the substrate surfaces.

Doped-Fluorine on Electrical and Optical Properties of Tin Oxide Films Grown by Ozone-Assisted Thermal CVD

Transparent conductive fluorine-doped tin oxide (FTO, ) films were grown using a low-pressure metallorganic chemical vapor deposition (LP-MOCVD) with tetramethyltin (TMT), oxygen containing ozone , and hydrofluoric acid (HF) as a dopant. Using ozone contained oxygen instead of pure oxygen, the substrate temperature could be reduced by while maintaining a growth rate similar to that of tin oxide film. Growth rate of FTO film increased with the flow rate of TMT, however, adherence strength between the film and glass decreased. Resistivity of FTO thin films decreased with the TMT and HF flows over most of ranges investigated, while the resistivity increased rapidly with respect to excessive flow of the TMT over 300 sccm. Optical transmittance of FTO film was about 80% at , and the variation as a function of HF flow rate was not significant. FTO film prepared at an optimum condition showed a minimum resistivity of , a mobility of , and a carrier concentration of .

MOCVD of Cr3 ( C , N ) 2 and CrSixCy Films: II. Properties as Conducting Cu Diffusion Barriers

Properties as conducting diffusion barrier against Cu of two types of original Cr-based thin films grown by low-pressure metallorganic chemical vapor deposition (MOCVD) on Si(100) and patterned substrates were investigated. Amorphous as-deposited and layers were deposited using and , respectively, as single-source precursor in the low-temperature range and . Then Cu films were grown on top of these barrier by low-pressure MOCVD using as molecular precursor. These structures were annealed under various conditions and they were thoroughly characterized in order to analyze the failure mechanism of the barrier. The barrier fails at due to the crystallization of the ternary compound . The barrier is more thermally stable and the failure temperature was found in the range due to Cu diffusion through the barrier and the formation of . The behavior of these two barriers is compared and their performances are discussed with literature data.

Mobility Enhancement and Breakdown Behavior in InP-Based Heterostructure Field-effect Transistor

This study proposes an heterostructure field-effect transistor (HFET) grown by a low-pressure metallorganic chemical vapor deposition system. Its InAlAsSb Schottky layer and coupled δ-doped InP channels cause this HFET to exhibit high two- and three-terminal breakdown voltages. Mobility and two-dimensional electron gas concentration are increased. Additionally, this HFET does not exhibit the frequently observed parallel conduction and bell-shaped characteristics of conventional HFETs. The activation energy is also determined.

Formation of ZnSe1-xSx quantum dots under Volmer-Weber mode

ZnSe1−xSx quantum dots (QDs) grown directly onto GaAs substrates in Volmer–Weber (V–W) mode by low-pressure metallorganic chemical vapor deposition (MOCVD) are investigated. The value of x is determined by the photoluminescence (PL) spectra. The formation of QDs was confirmed by atomic force microscopy (AFM) images. When the growth duration is short, the surface of the substrate is full of pyramid-like dots; while increasing the duration, another kind of dome-like dots with larger size appear. Meanwhile, the density of the dots decreases with increasing growth duration. The above facts are explained systematically taking into account the surface free energy. The PL characteristics of the dots are also assessed. With increasing growth duration, the emission peak of the dots shows an obvious red-shift, which is due to a decrease in quantum confinement effect.

Reactive ion etching of GaN with BCl 3/SF 6 plasmas

Reactive ion etching (RIE) with BCl 3/SF 6 plasmas of high quality GaN films grown by low pressure metallorganic chemical vapor deposition (LP-MOCVD) is reported. A high etch rate of 2100 Å min −1 was achieved with BCl 3/SF 6 plasmas at gas pressure 40 mtorr, total gas flow rate 40 sccm, and radio-frequency (RF) power 300 W. The parameters affecting the etch rates such as BCl 3/SF 6 flow ratio, total gas pressure, RF power and self-bias voltage have been studied. Results indicate that under high RF power (300 W) the radical concentration is an etch rate-limiting factor at lower BCl 3/SF 6 pressure (lower than 40 mtorr), while self-bias voltage (ion bombardment) is a rate-limiting factor at higher pressure (more than 40 mtorr). Under lower RF power (150 W), self-bias voltage becomes the dominant factor of etch rate. Scanning electron microscopy (SEM) shows that the etched profile is highly anisotropic, and the etched area has some columnar residues due to Al compound contamination from the Al cathode during RIE.

TP-B2 room-temperature of a GaInAsP/InP double-heterostructure laser grown by low-pressure metallorganic chemical-vapor deposition

TP-B2 room-temperature of a GaInAsP/InP double-heterostructure laser grown by low-pressure metallorganic chemical-vapor deposition