Pn Junction Formation Research Articles

Fabrication of Thin-Film Polycrystalline Silicon Solar Cells by Silane-Gas-Free Process Using Aluminum-Induced Crystallization

The authors have proposed a silane-gas-free fabrication process for thin-film polycrystalline Si solar cells. The process includes formation of a polycrystalline Si seed layer by aluminum-induced crystallization (AIC), crystallization of a Si film formed by physical vapor deposition (PVD) techniques for a base layer, aluminum diffusion from the AIC-grown Si (AIC-Si) layer to the base layer and pn-junction formation by the spin-on-glass technique. The crystal grains grew to a size of ∼20 µm in diameter through crystallization of the electron-beam-evaporated Si film on the AIC-Si layer, and the carrier lifetime was about 0.6 µs. In the solar cell fabricated by this process, the AIC-Si layer acts as a back-surface-field (BSF) layer, and the energy band is also inclined in its base layer so that the minority carriers can be pushed back to the depletion layer. These features indicate the possibility of fabricating low-cost and high-efficiency thin-film polycrystalline Si solar cells. The issues that must be pursued to realize high efficiency are reduction of oxygen atom inclusions during Si film deposition, passivation of the grain boundaries and development of a deposition technique for Si films having intermediate packing densities between those of electron-beam-evaporated films and sputter-deposited films, to prevent crack formation when the Si films are crystallized.

Long-pulse duration excimer laser annealing of Al + ion implanted 4H-SiC for pn junction formation

As an alternative to classical thermal heating, laser annealing (LA) was recently demonstrated to be suitable for the electrical activation of ion-implanted dopants in SiC. In this work, we demonstrate the possibility to anneal the Al + ion-implantation induced damage into 4H-SiC by solid phase laser processing using a XeCl excimer source of 200 ns-pulse duration. The electrical activation of the Al dopant was confirmed by I– V measurements performed directly on mesa pn junction diodes.

SiCへの高エネルギーAl、Bイオン注入による深い接合の形成

SiCへの高エネルギーAl、Bイオン注入による深い接合の形成

Highest efficiency rapid thermal processed multicrystalline silicon solar cells

AbstractThe formation of pn junctions and surface passivation by rapid thermal processing is being proved as a new and competitive method for silicon solar cell production. As the main process mechanisms are enhanced, the total process time at high temperature can be kept in the minute range, for the realization of emitter, back surface field (BSF) and surface passivation. In this work, we demonstrate for the first time that this knowledge, avoiding any in‐situ annealing step acquired on the sc‐Si, can also be applied on industrial mc‐Si (Polix©) without bulk degradation, leading to a record conversion efficiency of 16·7%. Copyright © 2001 John Wiley & Sons, Ltd.

Formation of Deep pn Junctions by MeV Al- and B-ion Implantations into 4H-SiC and Reverse Characteristics

Formation of Deep pn Junctions by MeV Al- and B-ion Implantations into 4H-SiC and Reverse Characteristics

Rapid thermal processing for high efficiency silicon solar cells

The formation of pn junctions and surface passivation layers by rapid thermal processing is opening new possibilities for a low-cost and environmentally safe silicon solar cell production. As the main process mechanisms like the diffusion of different dopants and the oxidation of the silicon surface are enhanced, the total process time at high temperature can be kept in the magnitude of one minute, for the realization of emitter, back surface field (BSF) and surface passivation. The surface concentration of the diffused junction is revealed as one of the major parameters to be controlled during the diffusion process, in order to obtain suitable front surface recombination velocities. Simultaneous diffusion of phosphorus and aluminum is used to realize the emitter and back surface field in a single high-temperature step, with optimized gettering effect. During this step the gettering efficiency is given by the formation of a silicon-aluminum alloy, opening the possibility to apply different phosphorus sources to control the emitter surface concentration. Reduced surface recombination velocities and controlled bulk diffusion lengths are observed. Controlling the mentioned parameters on industrial 1 cm CZ material led to 17.5% efficient solar cells on a surface of 25 cm2.

A Historical View of the Role of Ion-Implantation Defects in PN Junction Formation for Devices

AbstractThe early use of ion bombardment of semiconductors for forming doped regions was viewed as a room-temperature process by solid-state scientists. Many interesting, but relatively useless devices were made by implanting species such as Na and Cs ions to form pn junctions from radiation damage or interstitial impurities. The revolutionary idea that one could implant Group III and V dopants into semiconductors and then heat the implanted substrate to above 800C didn't appear until 10 years after Shockley's 1954 patent. At that time, implantation damage became relatively unimportant as processes evolved with high temperature, long time diffusions. With the advent of rapid thermal processing, the attention shifted back to implantation-induced defects to explain transient-enhanced-diffusion effects. Today's challenges in forming ultra-shallow junctions by ion-implantation are in controlling and minimizing the damage structures that dominate junction activation and diffusion. Low-energy implants have been effective in this regard.

Characterization of silicon LEDs integrated with oxidized porous silicon SOI

Slightly modified CMOS process has been used for the formation of lateral pn junctions in SOI structures based on oxidized porous silicon. Under forward bias these junctions emit infrared light at 1120 nm. Under reverse bias in the breakdown regime the pn junctions demonstrate both infrared and visible light emissions with efficiencies of 10 −4 and 10 −7, respectively. The beneficial influence of SOI structures on electroluminescence characterictics of light-emitting pn junctions has been established.

GaAs side-by-side direct wafer bonding and formation of lateral pn junction

We demonstrate the first successful side-by-side lateral wafer bonding of GaAs which is expected to increase the flexibility of the device fabrication process. First we give a brief review of compound semiconductor surface-to-surface direct wafer bonding, which has been remarkably successful in device applications owing to a new dimension in the fabrication process flexibility. Then results of side-by-side direct wafer bonding, which was achieved using a pair of cleaved facets taking advantage of their quasi-perfect flat surfaces, are presented. It is shown that submicron-order leveling can be easily achieved by face-down alignment of the two wafers. Lateral nn and pn junctions have been successfully formed using bulk substrates and even with epitaxial wafers. Current-voltage characteristics across the bonded interface show that no observable electrical barrier is formed by the bonding process. Although some oxides were found to exist at the bonded interface, TEM measurements revealed that atomic-order recrystallization is achieved in most of the interface after heat treatment at 700°C for 30 min.

Formation of pn junctions by bonding of GaAs layer onto diamond

Direct bonding of an n-GaAs thin film onto the surface of epitaxial p-diamond has been attempted. Prior to bonding, the diamond and GaAs surfaces were analyzed by X-ray photoelectron spectroscopy. A rectifying characteristic was obtained for the p-diamond/n-GaAs bonded junction system. Moreover, the occurrence of a photovoltaic effect at the junction was observed under illumination with a AlGaAs laser operated at 789 nm. Thus a Diamond-GaAs pn junction can be formed by direct bonding.

Thin film photodetectors grown epitaxially on silicon

Abstract Epitaxial germanium films of thickness d≈4 μ m , grown on silicon (001) by a low-temperature MBE process, constituted the base material of a silicon-integrated infrared detector. Characterization of the fully relaxed films was performed mainly by ex situ techniques, such as X-ray diffraction, Rutherford backscattering spectrometry and channeling, room temperature Hall effect and defect etching. Mesa diodes, fabricated from the originally p-type Ge films after pn-junction formation by thermal diffusion of antimony (Sb), showed quantum yields above 40% at wavelengths between 1200 nm and 1500 nm without an antireflection coating. The rise time of the photodiode signal in response to a picosecond laser pulse ( τ = 300 ps ) at wavelength of 1300 nm was 530 ps. Forward current-voltage characteristics of the devices were described by an ideality factor n = 1.25 , while excess current under reverse bias was attributed to leakage caused by threading dislocations in the active layers.

PN Junction Formation by Two Steps Annealing

PN Junction Formation by Two Steps Annealing

Temperature Dependent Current-Voltage Characteristics of TiSi2/n+/p-Si Shallow Junctions

ABSTRACTModelling of temperature dependent current-voltage characteristics of TiSi2/n+/p-Si shallow junctions has been presented here. The formation of shallow pn junctions, by ion implantation of As+ through Ti films evaporated on p-Si substrates has been performed in these experiments. The temperature dependent factors such as band gap narrowing, intrinsic carrier concentration, mobilities and diffusivities are considered in the model.

Simultaneous annealing for implantation activation and spin-on source diffusion into GaInAs: A novel approach for the formation of p n junctions

A new process—simultaneous implantation and diffusion annealing—has been developed for the formation of pn junctions in compound semiconductors. It combines implantation and diffusion, by using doped SiO2 spin-on films simultaneously as a surface protection during activation of the implants and as a diffusion source. Only a single annealing step is necessary, which is very important for a careful heat treatment of existing semiconductor structures. Examples are presented for GaInAs. The n level formed by Si implantation varies from 1×1017 cm−3 to 6×1018 cm−3, with an increasing dose. The p level is adjusted to about 1×1019 cm−3 by the amount of Zn salt in the spin-on solution. The position of the pn junction is shifted by the annealing step.

4970. Pn junction formation in CdTe by ion implantation and pulsed ruby laser annealing: C B Norris et al, Rad Effects, 58 (3), 1981, 115–117

4970. Pn junction formation in CdTe by ion implantation and pulsed ruby laser annealing: C B Norris et al, Rad Effects, 58 (3), 1981, 115–117

PN junction formation in CdTe by ion implantation and pulsed ruby laser annealing

PN junction formation in CdTe by ion implantation and pulsed ruby laser annealing

Formation of pn Junction by Ion Beam Implantation

The heavy ion beam of Boron and Phosphorus are implanted to Silicon substrate and the pn junctions are formed. The depth of the pn junctions are measured and are compared with the calculated results which are derived from the universal range energy relation due to Lindhard theory. The results fairly good agreement. The technique is applied to produce the mesa type diode, and the characteristics of the diode are fairly good. The channeling, the sputtering, and the damage which are produced by the ion implantation to the Silicon substrate are also discussed.

ELECTRON PARAMAGNETIC RESONANCE IN NON-IRRADIATED BONE.

THE generation of electrical potentials by bone subjected to mechanical stress has been recently reported by two groups of investigators1,2. Bassett and Becker suggested a semiconduction mechanism as being the source of the phenomenon, while Shamos et al. favoured a classical piezo-electric mechanism similar to that earlier described by Fukada and Yasuda3. The semiconduction theory has recently been reported on in more detail4 and evidence presented for the formation of multiple pn junctions from the apatite crystal (p type) collagen fibre (n type) in the bone matrix. Similar inorganic pn junctions have been shown to be exceedingly stress sensitive5,6.