Phosphine Flow Rate Research Articles

Impact of the n+ emitter layer on the structural and electrical properties of p-type polycrystalline silicon thin-film solar cells

The effect of the phosphine (PH3) flow rate on the doping profile, in particular the peak doping concentration of the n+ emitter layer, of solid phase crystallised polycrystalline silicon thin-film solar cells on glass is investigated by electrochemical capacitance-voltage profiling. The peak n+ layer doping is found to increase with increasing PH3 gas flow, resulting in a shift of the p-n junction location towards the centre of the diode. The impact of the PH3 flow rate on the crystal quality of the poly-Si films is analysed using ultraviolet (UV) reflectance and UV/visible Raman spectroscopy. The impact of the PH3 flow rate on the efficiency of poly-Si thin-film solar cells is investigated using electrical measurements. An improvement in the efficiency by 46% and a pseudo energy conversion efficiency of 5% was obtained through precise control of the flow rate at an intermediate n+ emitter layer doping concentration of 1.0 × 1019 cm−3. The best fabricated poly-Si thin-film solar cell is also found to have the highest crystal quality factor, based on both Raman and UV reflectance measurements.

A delta-doped amorphous silicon thin-film transistor with high mobility and stability

Ultrathin doped layers, known as delta-doped layers, were introduced within the intrinsic amorphous silicon (a-Si) active layer to fabricate hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) with enhanced field-effect mobility. The performance of the delta-doped a-Si:H TFTs depended on the phosphine (PH3) flow rate and the distance from the n+ a-Si to the deltadoping layer. The delta-doped a-Si:H TFTs fabricated using a commercial manufacturing process exhibited an enhanced field-effect mobility of approximately ∼0.23 cm2/Vs (compared to a conventional a-Si:H TFT with 0.15 cm2/Vs) and a desirable stability under a bias-temperature stress test.

Emission characteristics of CuGaS 2-based light-emitting diode grown by metalorganic vapor phase epitaxy

Phosphorus-doped CuGaS 2 layers were grown on (001) GaP substrates by metalorganic vapor phase epitaxy. The p-type conductivity was controllable under the phosphine flow rate conditions. The rectification characteristics of a p-CuGaS 2/n-GaP heterostructure indicated that the p–n junction was formatted. Orange light electroluminescence was observed from the CuGaS 2-based diode at room temperature.

Competition between As and P for incorporation during gas-source molecular beam epitaxy of InGaAsP

It is now well established that arsenic sticks predominantly over phosphorus during gas-source molecular beam epitaxy of InGaAsP. Although not the main parameter, the actual value of the phosphine flow rate, however, cannot be neglected when a precise alloy composition is desired. We show that the arsenic content in the solid is proportional to an effective flow rate, which is lower than the actual flow rate and is obtained after correcting for competing effects. Two effects are evidenced in this study: first, an As–P competition and second, an As–As competition which becomes sensitive for high arsine flow rates. These corrections to obtain an effective arsine flow rate are investigated quantitatively for arsenic composition ranging from 0% to 65%. These competitions for incorporation are shown to be a purely group V effect, independent of the Ga/In ratio.

Relationship between surface reconstruction and morphology of strained Ga1−xInxP layers grown on GaP (001) by gas-source molecular-beam epitaxy

We study the growth of strained Ga1−xInxP layers on GaP (001) by gas-source molecular-beam epitaxy for x varying from 0.25 to 1. At a growth temperature of 520 °C, we find two main differences with respect to the well known GaInAs/GaAs system. First, for 0.25⩽x⩽0.5, we observe the development of wire-like structures oriented along the [110] direction and on the other hand, the growth of InP on GaP leads to the formation of huge dots in small density. The influence of the growth parameters such as the growth temperature or the phosphine flow rate is presented. The whole set of results is discussed in light of recent work on the phosphide surface reconstructions with a particular emphasis on the role of the cation-rich one.

Influence of phosphine flow rate on Si growth rate in gas source molecular beam epitaxy

As reported by other authors, we have also observed that the Si growth rate decreases with increasing phosphine (PH 3) flow rate in gas source Si molecular beam epitaxy using phosphorous (P) as a n-type dopant. Why small quantity PH 3 can affect Si growth rate? Up to now, the quantitative characterization of PH 3 flow influence on Si growth rate is little known. In this letter, the PH 3 influence will be analyzed in detail and a model considering strong P surface segregation and its absorption of hydrogen will be proposed to characterize the effect.

Sb-flow-rate dependence of triple-period (TP)-A-type atomic-ordering in Ga 0.5In 0.5P grown by metalorganic-vapor-phase epitaxy

The Sb-flow-rate dependence of atomic ordering in Ga 0.5In 0.5P grown at about 650°C on (0 0 1) GaAs substrates by metalorganic-vapor-phase epitaxy was studied. The Sb-flow-rate ratio f R (defined as [TDMASb]/([PH 3]+[TDMASb])) was varied in a small Sb-flow-rate-ratio regime ( f R⩽1%), where [TDMASb] and [PH 3] indicate the Sb-source-gas (TDMASb: Tris-dimethy-lamino-antimony) flow-rate and phosphine flow-rate, respectively. CuPt-B-type atomic ordering appeared for 0%⩽ f R⩽0.015%. For f R≈0.015%, a mixture of CuPt-B and TP (triple-period)-A ordering domains is formed, while for f R⩽0.05%, TP-A ordering was dominant. Based on these results, it was concluded that the surface structure changed from (2×1) to (2×3) in-between f R=0.015% and 0.05%. The Sb-composition in solid ((1− y) Sb, where 1− y is that in Ga 0.5In 0.5P y Sb 1− y ) tended to saturate for f R⩾0.05%. It is noted that TP-A-type ordering appeared in the Sb-composition saturation regime; (1– y) Sb was 0.73% at f R≈0.050% and, 1.6% at f R≈1.0%, respectively. Thus, Sb incorporation appears to be influenced by the surface reconstruction.

Phosphorus Doping and Sharp Profiles in Silicon and Silicon‐Germanium Epitaxy by Rapid Thermal Chemical Vapor Deposition

In situ phosphous doping of silicon epitaxy from 700 to 1000°C by low pressure rapid thermal chemical vapor deposition in a cold wall system, using dichlorosilane as the silicon source, has been investigated. At a high phosphine flow rate, the growth rate of silicon decreases dramatically (by ∼60%) and the phosphorus incorporation level saturates. A significant persistence effect of phosphorus after turning off phosphine is observed. However, a sharper transition and higher doping level are observed in layers grown at 625°C. Improvement of the phosphous profile in silicon to ∼ 13 nm/decade is demonstrated by reactor cleaning and ex situ etching of the wafer surface during a growth interruption after phosphorus‐doped epitaxy. Despite the growth interruption, an in situ 800°C bake at 10 Torr in hydrogen before regrowth can give an oxygen‐ and carbon‐free interface without excessive dopant diffusion. © 2000 The Electrochemical Society. All rights reserved.

Compositional Ordering in GalnP for Heterostructure Formation

AbstractCompositional ordering is observed in essentially all IIIN semiconductor alloys. The mechanism leading to the specific ordered structures formed is only now beginning to be understood. It is intimately related to the atomic-scale physical processes occurring on the surface during epitaxial growth, specifically surface reconstruction and the attachment of atoms at steps. This paper will emphasize the use of surface analytic techniques to better understand the ordering processes during organometallic vapor phase epitaxial growth of GalnP. Surface photo absorption has been used to determine, for the first time, that the surface reconstruction is (2×4)-like during growth of GalnP with Cu-Pt ordering. By increasing the growth temperature and/or decreasing the V/Ill ratio the concentration of phosphorus dimers characteristic of the (2×4) structure is observed to decrease in tandem with a decrease in the degree of order measured in the epitaxial layers. This suggests that formation of the (2×4) reconstruction is necessary for formation of the Cu-Pt ordered structure.Atomic force microscopy was used to examine the step structure. For exactly (001)-oriented substrates, growth at low V/Ill ratios produces islands surrounded by single monolayer steps. Increasing the V/Ill ratio leads to the formation of bilayer steps approximately 6 Å high. A similar change in the structure of steps is observed in the vicinal regions for substrates misoriented to produce [110] steps. This phenomenon is interpreted in terms of the stabilization, at high V/Ill ratios, of the (2×2) reconstruction on the (111)B regions of the bilayer steps. This may also have an effect on formation of the Cu-Pt ordered structure.By changing the substrate temperature or the input partial pressure of the phosphorus precursor, the degree of order and, hence, the bandgap energy of GalnP, can be modulated during growth. This has allowed the production of a variety of single and double heterostructures. The heterostructures produced by changing the temperature from 740 to 620°C and from 620 to 520°C are abrupt. The heterostructures formed by changing the phosphine flow rate are not. The ordered structure in the lower layer persists into the upper layer. This may be an indication of the importance of the step structure.

In situ control of As composition in InAsP and InGaAsP grown by gas-source molecular beam epitaxy

Group-III- and group-V-induced intensity oscillations of reflection high-energy electron diffraction are observed for InAsP in gas-source molecular beam epitaxial growth. The As incorporation rate is found to be dominant, independent of the presence of P when the phosphine flow rate is reasonably low. This observation suggests a simple method of controlling the As composition in InAsP by just controlling the incorporation-rate ratio of As to In when this ratio is less than unity. This successful in situ composition control for InAsP, combined with the in situ composition calibration in GaAsP reported previously, provides a general guideline for controlling the compositions in InGaAsP.

Kinetic study of metalorganic molecular beam epitaxy of GaP, InP, and GaxIn1−xP

The growth rates of GaP and InP deposited by metalorganic molecular beam epitaxy using triethylgallium, trimethylindium, and precracked phosphine have been studied by reflection high energy electron diffraction and related to composition variations of the ternary alloy GaxIn1−xP. The influence of the substrate temperature and phosphine flow rate have been investigated for each material. The GaP growth rate dependence with temperature exhibits qualitatively the same behavior as already reported for the growth of GaAs by metalorganic molecular beam epitaxy. In the case of InP, a constant growth rate is observed in the temperature range of 450–500 °C. At higher temperatures, a strong decrease of the growth rate, attributed to the desorption of dimethylindium species, is measured. Meanwhile, the GaxIn1−xP composition is found to become Ga rich while increasing temperature. Furthermore, it is found to significantly depend on the phosphine flow rate at a fixed temperature. In the low phosphine flow regime, the composition is associated with the preferential formation of GaP bonds, and in the high phosphine flow regime, the composition is closely correlated with the sharp decrease observed for the binary InP growth rate.

Reflection High-Energy-Electron Diffraction Study of Inp and InAs (100) In Gas-Source Molecular Beam Epitaxy

ABSTRACTInP and InAs (100) were grown by gas-source molecular-beam epitaxy (GSMBE) with arsine, phosphine, and elemental indium. Reflection high-energy-electron diffraction (RHEED) was used to monitor surface reconstructions and growth rates. (2×4) to (2×1) transition was observed on InP (100) as phosphine flow rate increased. (4×2) and (2×4) patterns were observed for In-stabilized and As-stabilized InAs surfaces, respectively. Both group-V and group-rn-induced RHEED oscillations were observed. The group-V surface desorption activation energy were measured to be 0.61 eV for InP and 0.19 eV for InAs. By this growth rate study, we are able to establish a precise control of V/HII atomic ratios in GSMBE of InP and InAs.