Deep centers investigations of P-HEMT functional materials of ultra-high-speed microstructures grown by MBE

The deep centers of high electron mobility transistor (HEMT) and pseudomorphic-HEMT (P-HEMT) functional materials of ultra-high-speed microstructures grown by MBE are investigated using deep level transient spectroscopy (DLTS) technique. DLTS spectra demonstrate that midgap states, having larger concentrations and capture cross sections, are measured in n-AlGaAs layers of HEMT and P-HEMT structures. These states may correlate strongly with oxygen content of n-AlGaAs layer. At the same time, one can observe that the movement of DX center is related to silicon impurity that is induced by the strain in AlGaAs layer of the mismatched AlGaAs/InGaAs/GaAs system of P-HEMT structure. The experimental results also show that DLTS technique may be a tool of optimization design of the practical devices.

Electroluminescence from Au/(SiO2/Si/SiO2) nanometer double barrier/p-Si structures and its mechanism

SiO2/Si/SiO2 nanometer double barriers (SSSNDB) with Si layers of twenty-seven different thicknesses in a range of 1-5 nm with an interval of 0.2 nm have been deposited on p-Si substrates using two-target alternative magnetron sputtering. Electroluminescence (EL) from the semitransparent Au film/SSSNDB/p-Si diodes and from a control diode without any Si layer have been observed under forward bias. Each EL spectrum of all these diodes can be fitted by two Gaussian bands with peak energies of 1.82 and 2.25 eV, and full widths at half maximum of 0.38 and 0.69 eV, respectively. It is found that the current, EL peak wavelength and intensities of the two Gaussian bands of the Au/SSSNDB/p-Si structure oscillate synchronously with increasing Si layer thickness with a period corresponding to half a de Broglie wavelength of the carriers. The experimental results strongly indicate that the EL originates mainly from two types of luminescence centres with energies of 1.82 and 2.25 eV in the SiO2 barriers, rather than from the nanometer Si well in the SSSNDB. The EL mechanism is discussed in detail.

Carrier transport properties of the (n)nc-Si : H/(p)c-Si heterojunction

Phosphor-doped nano-crystalline silicon ((n))nc-Si:H) films are successfully grown on the p-type (100) oriented crystal silicon ((p) c-Si) substrate by conventional plasma-enhanced chemical vapor deposition method. The films are obtained using high H-2 diluted SiH4 as a reaction gas source and using PH3 as the doping gas source of phosphor atoms. Futhermore, the heterojunction diodes are also fabricated by using (n)nc-Si:H films and (p)c-Si substrate. I-V properties are investigated in the temperature range of 230-420K. The experimental results domenstrate that (n)nc-Si:H/(p) c-Si heterojunction is a typical abrupt heterojunction having good rectifing and temperature properties. Carrier transport mechanisms are tunneling - recombination model at forward bias voltages. In the range of low bias voltages ( V-F< 0.8 V), the current is determined by recombination at the (n)nc-Si:H side of the space charge region, while the current becomes tunneing at higher bias voltages( V-F>1.0 V). The present heterojunction has high reverse breakdown voltage ( > - 75 V) and low reverse current (approximate to nA).

1.5 mu m luminescence characteristic of erbium in B, P doped a-SiO : H films

Hydrogenated amorphous silicon films co-doped with oxygen (O), boron (B) and phosphorus (P) were fabricated using PECVD technique. The erbium (Er) implanted samples were annealed in a N-2 ambient by rapid thermal annealing. Strong photoluminescence (PL) spectra of these samples were observed at room temperature. The incorporation of O, B and P could not only enhance the PL intensity but also the thermal annealing temperature of the strongest PL intensity. It seems that the incorporation of B or P can decrease the grain boundary potential barriers thus leading to an easier movement of carriers and a stronger PL intensity. Temperature dependence of PL indicated the thermal quenching of Er-doped hydrogenated amorphous silicon is very weak.

Temperature dependence of photoluminescence of an n-i-p-i GaAs superlattice

Both the photoluminescence peaks corresponding to the vertical transitions and the nonvertical transitions in an n-i-p-i GaAs superlattice are clearly observed. The redshifts of the two peaks with increasing temperature are: discussed in terms of the temperature-dependent carrier separation effect.

Photoluminescence of InAs quantum dots in n-i-p-i GaAs superlattice

Large blueshift and linewidth increase in photoluminescence (PL) spectra of InAs quantum dots (QD's) in n-i-p-i GaAs superlattice were observed. By increasing the excitation intensity from 0.5 to 32 W/cm(2), the PL peak position blueshifted 18 meV, and the linewidth increased by 20 meV. Such large changes are due to the state-filling effects of the QD's resulted from the separation of photogenerated electrons and holes caused by the doping potential.

Optical properties of InAs self-organized quantum dots in n-i-p-i GaAs superlattices

The optical properties of InAs quantum dots in n-i-p-i GaAs superlattices are investigated by photoluminescence (PL) characterization. We have observed an anomalously large blueshift of the PL peak and increase of the PL linewidth with increasing excitation intensity, much smaller PL intensity decrease, and faster PL peak redshift with increasing temperature as compared to conventional InAs quantum dots embedded in intrinsic GaAs barriers. The observed phenomena can all be attributed to the filling effects of the spatially separated photogenerated carriers. (C) 2000 American Institute of Physics. [S0003-6951(00)03515-4].

The new exploration for proton-implanted silicon: the conversion of a surface-region-purification-induced p-n junction into a p-i-n electrical structure approaching silicon on insulator

A surface-region-purification-induced p-n junction, a puzzle discovered at Brookhaven National Laboratory, in a silicon-on-defect-layer (SODL) material has been explored by carrying out various annealing conditions and subsequent measurements on electrical properties. The origin of the pn junction has been experimentally investigated. Furthermore, the p-n junction has been transformed into a p-i-n electrical structure by adding a high temperature annealing process to the previously used SODL procedure, making the SODL material approach silicon on insulator (SOI). The control of the initial oxygen amount in the silicon material is suggested to be critical for the experimental results.

Doping during low-temperature growth of materials for n-p-n Si/SiGe/Si heterojuction bipolar transistor by gas source molecular beam epitaxy

In situ doping for growth of n-p-n Si/SiGe/Si heterojuction bipolar transistor (HBT) structural materials in Si gas source molecular beam epitaxy is investigated. We studied high n-type doping kinetics in Si growth using disilane and phosphine, and p-type doping in SiGe growth using disilane, soild-Ge, and diborane with an emphasis on the effect of Ge on B incorporation. Based on these results, in situ growth of n-p-n Si/SiGe/Si HBT device structure is demonstrated with designed structural and carrier profiles, as verified from characterizations by X-ray diffraction, and spreading resistance profiling analysis. (C) 2000 Elsevier Science B.V. All rights reserved.

Properties of proton-implanted p-type Si: supports for the models explaining a novel p-n junction in Si

Proton-implanted and annealed p-type Si wafers were investigated by using both transmission electron microscopy and spreading resistivity probe. The novel pn junction [Li et al., Mat. Res. Sec. Symp, Proc. 396 (1996) 745], as obtained by using n-type Si subjected to the process as this work, was not observed in the p-type Si wafers in this work. A drop of superficial resistivity in the sample was found and is explained by the proposed models interpreting the novel pn junction. (C) 2000 Elsevier Science B.V. All rights reserved.

Observation of field-driven blue shift in delta-doped Si n-i-p-i multiple quantum wells

We report the observation of the field-driven blue shift at near absorption edge in the photo-current response spectra of delta-doped Si n-i-p-i multiple quantum wells due to the widening of the effective energy gap. This phenomenon differs from the observed results in GaAs/AlGaAs and GeSi/Si superlattices, because the physical mechanisms of forming energy band in these superlattice samples are different. Our experimental results are interpreted satisfactorily by the theoretical calculation. (C) 1999 Elsevier Science Ltd. All rights reserved.

Influence of crystal perfection on the reverse leakage current of the SiGe Si p-n heterojunction diodes

Double-crystal X-ray diffraction and I-V characterization have been carried out on the GSMBE grown SiGe/Si p-n heterojunction materials. Results show that the SiGe alloys crystalline quality and the misfit dislocations are critical influences on the reverse leakage current. The crystal perfection and/or the degree of metastability of the Sice alloys have been estimated in terms of the model proposed by Tsao with the experimental results. High-quality p-n heterojunction diodes can be obtained by optimizing the SiGe alloy structures, which limit the alloys in the metastable states. (C) 1999 Elsevier Science B.V. All rights reserved.

p-type co-doping study of GaN by photoluminescence

Photoluminescence measurements were performed on p-type co-doping effects of C, As, and Mg in GaN. The dopants were incorporated into GaN by ion implantation performed at 77 K. We find that the 3.42 eV luminescence line is sensitive to hole concentration, and propose that after cartful calibration the 3.42 eV line may be used as a probe to measure hole concentration in GaN. Simply doping one kind of accepters will not result in holes, while co-doping can substantially improve p-type doping efficiency. As + C and As + Mg co-doping induce an acceptor level of 180 meV above the valence band. Mg + C co-doping is the most promising method for p-type doping, the related acceptor level is determined to be as shallow as 130 meV. The improvement of the doping efficiency by co-doping is probably due to the decrease of the acceptor ionization energy. (C) 1999 Elsevier Science B.V. All rights reserved.

Molecular beam epitaxy growth of Iny2Al1-y2As/In0.73Ga0.27As/Iny1Al1-y1As/InP P-HEMTs with enhancement conductivity using an intentional nonlattice-matched buffer layer

Pseudomorphic Iny2Al1-y2As/In0.73Ga0.27As/Iny1Al1-y1As (y1 greater than or equal to 0.52) modulation-doped heterostructures with an intentional nonlattice-matched buffer layer were successfully grown by molecular beam epitaxy on (100)InP substrates. Fourier transform photoluminescence and double crystal x-ray diffraction measurements show a superior crystalline quality in the high In content channel, when In mole fraction increases from y1=0.52 to 0.55 in the Iny1Al1-y1As buffer layer. In this case, an increasing of 16.3% and 23.5% for conductivity (mu xn(s)) and mobility, related to the strain compensation in the In0.73Ga0.27As channel, was achieved, respectively, comparing to the structure containing a well-lattice matched buffer layer. With increasing the mismatch further (y1=0.58), a morphology with cross-hatched pattern was observed due to the onset of a large amount of misfit dislocations, and the electronic characterization is not able to be improved continuously. Because we can realize high quality strained P-HEMTs in a relative wide range of equivalent beam flux (EBF) ratios, the stringent control over the constant EBF is not indispensable on this In-based material system. (C) 1997 American Vacuum Society.

On the performance analysis and design of a novel shared-layer integrated devices using RCE-p-i-n-PD/SHBT - art. no. 67820J

We have explored the shared-layer integration fabrication of an resonant-cavity-enhanced p-i-n photodector (RCE- p-i-n-PD) and a single heterojunction bipolar transistor (SHBT) with the same epitaxy grown layer structure. MOCVD growth of the different layer structure for the GaAs based RCE- p-i-n-PD/SHBT require compromises to obtain the best performance of the integrated devices. The SHBT is proposed with super-lattice in the collector, and the structure of the base and the collector of the SHBT is used for the RCE. Up to now, the DC characteristics of the integrated device have been obtained.