摘要:

A kinetic model based on two elementary reaction steps was used for exploring the prospects of atomic layer epitaxy (ALE) on the (100) surface of group IV semiconductors using hydridic source gases. Equating the chemisorption step with depletion of active sites, and the molecular hydrogen desorption step with regeneration of active sites allowed first‐principles kinetic modeling of the trends in thin film growth, unencumbered by the lack of mechanistic details of chemisorption and surface decomposition. The combination of first‐order depletion and first‐order regeneration steps was found to be most favorable for achieving ALE type behavior. The model shows that the ALE window is highly sensitive to the duration of the depletion (chemisorption) cycle suggesting short duration and well defined pulses as the most effective method of source gas delivery. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115030

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A systematic study of the noise performances of polycrystalline silicon thin film transistors is presented. The drain current spectral density of these devices shows an evident 1/ fbehavior and scales, when operating in the linear regime, with the square of the mean value of the drain current. The origin of the noise can be ascribed to carrier number fluctuations related to the dynamic trapping and detrapping of the oxide traps. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115031

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Si1−xGexalloys grown by catalytical decomposition of a mixture of disilane and germane on Si(001) at 620 K and room temperature (RT) have been prepared and analyzedinsituwith surface techniques such as x‐ray and ultraviolet photoelectron spectroscopies (XPS and UPS), low energy electron diffraction (LEED), and x‐ray photoelectron diffraction (XPD). A comparison is made with the case of an undecomposed gas mixture under the same experimental conditions. We show that films prepared at RT are amorphous. Films prepared at 620 K are well ordered and exhibit sharp 2×1 LEED patterns. Films grown at RT and subsequently annealed at as high as 820 K have a poorer crystalline quality. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115032

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A novel structure of &bgr;‐SiC/p‐Si has been reported to emit visible electroluminescence (EL). The &bgr;‐SiC is grown directly on a Si substrate by rapid thermal chemical vapor deposition (RTCVD) technology. The mechanism of EL emission is shown as a porous silicon (PS) layer. The PS is formed unintentionally at &bgr;‐SiC/p‐Si interface owing to a large lattice mismatch (20%) between &bgr;‐SiC and Si substrates. In addition, the heterojunction diode exhibits excellent rectifying behavior. The ideality factornand rectification ratio at 1.0 V are 1.8 and 340, respectively.

ISSN:0003-6951    

DOI:10.1063/1.115033

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The energy barrier at heterojunctions can be minimized by introducing a parabolic grading potential. For ternary materials with a strong bowing effect in band gap energy, such as Zn(Se,Te), the composition must vary nonparabolically in order to have the required parabolic grading potential. In this letter, a new compositional grading style for Zn(Se,Te) graded band gap ohmic contacts top‐type ZnSe has been obtained through a simplified analytical model where both the bowing factor in ternary band gap energy and the change in electron affinity &khgr; with alloy composition are included. To show the effectiveness of the proposed grading style, it is compared with both parabolic and linear grading in numerical calculations. The specific contact resistance of the proposed optimized compositional grading is about two orders of magnitude lower than that of a linear grading over a grading distance of 170 to 310 A˚, and about one order of magnitude lower than that of a parabolic grading at a grading distance less than 220 A˚. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.115034

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The mechanism of thin (<8 nm) oxide growth on Si(100) has been studied by high‐resolution medium energy ion scattering in combination with oxygen isotope substitution in theT=800–900 °C and 0.1–1 Torr oxygen pressure regime. Isotopic labeling experiments demonstrate that the Deal–Grove model breaks down for these films. In addition to the traditional oxidation reaction at the Si/SiO2interface, two other spatially specific reactions take place during thermal oxidation: an exchange reaction at the oxide surface and an oxidation reaction in the near‐interfacial region. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115035

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

AlxGa1−xN were grown on (00.1) sapphire and (111) silicon substrates in the whole composition range (0≤x≤1). The high optical quality of the epilayers was assessed by room‐temperature optical absorption and photoluminescence measurements. Layers with higher Al composition are more resistive. Resistive AlxGa1−xN epilayers were successfully doped with Ge and free‐electron concentration as high as 3×1019cm−3was achieved. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115036

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Molecular beam epitaxy (MBE) GaAs grown in the intermediate temperature range of about 400 °C may provide combination of low lifetime, high resistivity, and high mobility. We compare current conduction in unannealed and annealed material grown at 400 °C by fabricating photodetectors on substrates grown between temperature ranges of 250–500 °C. The unannealed version of the device grown at 400 °C shows substantial difference of conduction properties in dark and under light. It is shown that while at low biases the unannealed material may be semi‐insulating, at high biases more current is conducted than in annealed material. We attribute this to the effect of intergap states on current conduction and suggest that defect state assisted tunneling is the dominant current transport mechanism in these ranges. Quenching of response by light suggests that occupancy of traps can eliminate their role in current conduction. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115037

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Nitrogen atoms were implanted into ZnSe layers which were grown by metalorganic chemical vapor deposition. The implanted crystals were thermally annealed in a nitrogen atmosphere. Photoluminescence spectra show an acceptor‐bound excitonic emission line (I1) and donor‐to‐acceptor pair (DAP) recombination emission, which reveal the activation of nitrogen atoms as shallow acceptors. An additional DAP emission was observed at 462 nm, which is often seen for ZnSe:N grown by molecular beam epitaxy. The selenium vacancy generation accelerates the occupation of nitrogen atoms at the selenium sites and the excess vacancy generation brings about the formation of deep donor complexes. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115038

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

III–V nitride semiconductors have great potential for optoelectronic and electronic devices due to their wide direct band gaps. Because GaN is chemically very stable, dry etching techniques must be established in order to fabricate devices. In this work, we report the reactive ion etching (RIE) of GaN using CHF3/Ar and C2ClF5/Ar plasmas. GaN films on (001) GaAs were grown by electron cyclotron resonance (ECR) plasma associated molecular beam epitaxy (MBE) and the films showed (0001)hexorientation along the surface normal. We used a Drytek DRIE‐184 rf plasma discharge RIE system with no ECR discharge or high energy Ar ion beam. The effects of rf plasma power, pressure, and gas flow rates on the etch rate were investigated and the surface contamination due to RIE was examined by XPS. The etch rate varied between 60 and 470 A˚/min. The conditions for etching were 100–500 W of rf plasma power, 60–300 mTorr of pressure, a CHF3or C2ClF5flow rate of 5–50 sccm and an Ar flow rate of 0–50 sccm. The highest etch rates were obtained with high rf plasma power and low pressure. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.115039

出版商:AIP    

年代:1995

数据来源: AIP