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FORMATION OF EL2, ASGA AND U BAND IN IRRADIATED GAAS : EFFECTS OF ANNEALING

Gallium arsenide (GaAs) which was grown by metallorganic chemical vapor deposition, doped n with silicon to 2×1015 cm−3, and irradiated at room temperature with 1 MeV neutrons in the fluence range 1012 cm−2 to 3×1015 cm−2, has been studied by deep level transient spectroscopy (DLTS) and by far infrared photoluminescence (PL) spectroscopy. We report the effect of annealing at 550 °C for 30 min, which, in irradiated GaAs, is to introduce the gallium vacancy (VGa). The DLTS signal at 780±40 meV, attributed to the EL2 deep level, has an introduction rate of about 3×10−2 cm−1 in the unannealed case, and 0.19±0.02 cm−1 in the annealed case. The PL signal at 702 meV has been attributed to a phonon‐assisted transition of the EL2 defect, a defect which has been identified as the isolated arsenic antisite (AsGa+). The PL peak increases in intensity up to fluences of 3×1013 cm−2, before decreasing at higher fluences. After annealing, its intensity increases up to fluences of 1015 cm−2, before decreasing at the highe...

Electrical and optical characterization of SiONC dielectric thin film deposited by polymer-source chemical vapor deposition

The electro-optical properties of SiONC dielectric thin films deposited by polymer-source chemical vapor deposition using an organosilane precursor has been investigated as a function of oxygen concentration in the films. SiONC thin films were characterized using capacitance-voltage (C-V), conductance-voltage (G-V), ellipsometry, and ultraviolet visible (UV-Vis) photospectroscopy. These measurements showed that the electro-optical properties of the films are greatly influenced by the atomic concentration of oxygen. The high frequency C-V measurement revealed a nearly ideal metal-oxide-semiconductor (MOS) structure behavior at high atomic concentration of oxygen (35 at. %). A relative dielectric constant as high as 6 is obtained at 10 kHz for samples with about 5 at. % of oxygen, which corresponds to high-k dielectric material. The interface trap density extracted from G-V measurement using Hill-Coleman method is as low as 3.2×1010 (cm−2 eV−1), making these films a viable high-k dielectric alternative to S...

Chemical and Structural Characterization of SiONC Dielectric Thin Film Deposited by PSCVD

Thin films of silicon oxynitrocarbide (SiONC) have been deposited on silicon by polymer-source chemical vapor deposition (PSCVD) using poly(dimethylsilane). The chemical and structural composition of these films have been investigated using Fourier transform infrared spectroscopy, elastic recoil detection spectroscopy (ERD), and X-ray photoelectron spectroscopy (XPS). ERD depth-profile analysis revealed a homogeneous film with uniform bulk concentrations for silicon, carbon, nitrogen, and oxygen. XPS analysis showed that nitrogen, oxygen, and carbon were all uniquely bonded to silicon. The oxygen nitrogen bonds were not observed in these films. XPS analysis also revealed the presence of carbon-carbon bonds associated with graphite. It was shown that the graphitic phase is limited to the surface layer of these films, and is due to unintentional carbonization at the end of the deposition process. The relatively low bulk atomic concentration of carbon in the SiONC thin films (∼ 1%) render these films a possible alternative to SiON, and could become very attractive for the fabrication of integrated optical waveguides, and as a dielectric material in variety of microelectronic and optoelectronic devices.

Interface state buildup by high‐field stressing in various metal‐oxide‐semiconductor insulators using deep level transient spectroscopy

The buildup of interface states with high field (HF) stressing have been observed in thermally grown oxide, N2O nitrided oxide (NO), and reoxided nitrided oxide (RNO). The DLTS technique was used to analyze the electronic properties of the Si/SiO2 interface. We show that N2O nitridation of SiO2 changes the electronic distribution of states at the Si/SiO2 interface after HF electrical stress. Our results indicate that this nitrogen plays an important role in preventing the creation of a center at Et1=0.34 eV below the bottom of the conduction band. However, the nitrogen is responsible for a new level at Et2=0.22 eV below the bottom of the conduction band after the NO device is stressed. Also, reoxidation and increasing time of the reoxidation shift the maximum of the peak level away from the Et2 toward Et1.

Se chemical passivation and annealing treatment for GaAs Schottky diode

A Se chemical passivation [(NH4)2S+Se] for GaAs Schottky diodes is presented. We have found that our (NH4)2S+Se passivated Schottky diodes have more than one order of magnitude higher forward current density than the (NH4)2Sx passivated ones. In rapid thermal annealing treatment, an initial decrease and then increase of forward current density for (NH4)2Sx passivated diodes is observed. For the (NH4)2S+Se and (NH4)OH treated diodes, a steady decrease of Schottky barrier height with increased annealing temperature is observed. With or without annealing treatment, the (NH4)2S+Se passivated diodes have the lowest barrier height.

GaAs surface chemical passivation by (NH4)2S+Se and the effect of annealing treatments

Abstract We report on a new Se chemical passivation [(NH4)2S + Se] for GaAs surfaces. We compare our Se passivated surfaces with (NH4)2S + S [(NH4)2Sx] passivated surfaces by preparing Al-nGaAs Schottky diodes and submitting them to cumulative annealing treatments. We find that with or without an annealing treatment the Schottky barriers are consistently closer to the ideal value (0.2 eV) when the GaAs surfaces are treated with the (NH4)2S + Se rather than the (NH4)2Sx chemical solution. This indicates that (NH4)2S + Se surface passivation is more effective in reducing the surface state density and in unpinning the Fermi level than the (NH4)2Sx passivation treatment. These results are attributed to the complementary passivation role of the S and the Se on the GaAs surface. Also, the annealing treatment plays an important role in the control of the barrier height in both kinds of passivation.

Fabrication and Characterization of GaAs MOS Capacitor With CVD Grown Polymer-Based Thin Film as a Gate Dielectric

GaAs Metal-Oxide-Semiconductor (MOS) capacitor using a polymer-based thin film as a gate dielectric has been fabricated and electrically characterized. The influence of the atomic concentration of oxygen in the dielectric films on the capacitance-voltage (C-V) and current-voltage characteristics of the MOS capacitors has been thoroughly investigated. The GaAs MOS capacitor obtained at low concentration of oxygen showed an almost ideal MOS capacitor behavior. The density of the interface traps extracted from the conductance-frequency measurement was found to be as low as 9.7 x 109 eV-1 cm-2. In addition, the MOS capacitor exhibits very low leakage current (6.6 10-9 A/cm2 at -1 V) and relatively high breakdown voltage (2.05 MV/cm). These characteristics make polymer-based thin films very attractive as a passivation layer and a gate dielectric for GaAs MOSFET. The ability to tune the polymer through chemical synthesis and polymer functionalization makes CVD grown polymer-based thin films very promising for the passivation of virtually any semiconductor surface.

A simple velocity model for low‐pressure metalorganic chemical vapor deposition

A new simple transport model is used to describe the dependence of the electrical characteristics of the epitaxial layer on the growth parameters in low‐pressure metalorganic chemical vapor deposition. The important parameters of this model are the mean velocity of the gases and the [V]/[III] ratio. Undoped GaAs epitaxial layers are prepared at various operating pressures. A semi‐empirical correlation relating the reactor pressure and flow rate is established that dictates the operating conditions for a single set of film properties. This enables growth of a material with constant characteristics while pressure can be varied.