Determination of the diffusion length of charge minority carriers using digital oscillography of surface photovoltage

A procedure for determining the diffusion length of charge minority carriers (CMCs), which uses digital oscillography to detect surface photovoltage (SPV), is considered. It is shown by experiments that the shape of pulses of SPV, excited by rectangular IR pulses, depends significantly on both their intensity and wavelength. It is shown that it is not valid to use a synchronous detector to measure the quasi-stationary SPV when determining the diffusion length of CMCs in semiconductors, because, in a number of cases, it results in an uncontrollable error that reaches 100% and more. A technique is developed for determining the diffusion length in silicon wafers and epitaxial structures with the specific resistance range 0.01–12 Ω cm, the diffusion length range 5–500 μm, and an error of not more than 8%.     

EBIC测定GaP LPE样片的少子扩散长度

少数载流子扩散长度(L)是半导体材料的一个重要参量,它反映了晶体的完整性,与晶体的结晶质量、掺杂及晶体缺陷等有关.扫描电子显微镜(SEM)的电子束感生电流(EBIC)被广泛地用于测定少子扩散长度,其优点是通过改变电子束的加速电压,就能精确地控制激发源的大小和深度,从获得的EBIC扫描曲线,拟合得到L值[1～3].GaP是目前商用绿色LED的主要材料,市场需求量很大,但对其重要参量少子扩散长度的测量却很少.本工作利用EBIC对一组GaP绿色LED用LPE样片进行少子扩散长度测量.     

Measurement of Richardson constant of GaAs Schottky barriers

The Richardson constants for near-ideal AuGaAs and AlGaAs Schottky diodes have been determined from an analysis of forward current-voltage characteristics. Measurement of capacitance-voltage characteristics at different temperatures shows that the barrier heights of the diodes have very similar temperature dependence for both Au and Al contacts. On taking into account the temperature dependence of the barrier height, the corrected value of the Richardson constant for AuGaAs diode is found to be very close to the predicted theoretical value. The corresponding value for AlGaAs diode is about a factor of five smaller which is explained on the basis of a thin interfacial layer between Al and GaAs.     

Photoelectric C-V profiling of majority charge carriers and effective lifetimes of minority charge carriers in gettered GaAs wafers

The procedure for photoelectrochemical C-V profiling of the concentration of majority charge carriers and effective lifetimes of minority charge carriers in high-resistivity thick (1.6 mm) GaAs wafers subsequently to their gettering is described. Gettering was performed by both one-side and two-side coating of the wafers with a Y film and subsequent thermal treatment at 700 and 800°C. It was demonstrated that the concentration profile N _d-N _a and the effective lifetime for minority charge carriers throughout the wafer are rather uniform in both cases. This procedure makes it possible to measure the charge carrier concentration as low as 10¹² cm^?3.     

Schottky rectifiers on silicon using high barriers

Schottky diodes are presently used for power rectification because of their low forward voltage drop. However, they have only been fabricated on relatively low resistivity and thin semiconductor layers. Hence the reverse breakdown voltages are low. To make diodes that stand higher reverse voltages, low doped material of sufficient thickness is necessary. Ordinary Schottky barriers do not inject minority carriers and the resistive voltage drop at high forward currents will be large, However, for high Schottky barriers ～ 0.9eV, minority carriers are injected and the series resistance is decreased.In this paper we report results from one-dimensional numerical calculations as well as experimental results of high barrier Schottky diodes. We discuss the voltage drop at high forward currents for different substrate resistivity and thickness, as well as values of the high barrier.     

Measurement of minority carrier lifetime and diffusion length in silicon epitaxial layers by means of the photocurrent technique

A new method for the determination of minority carrier lifetime and diffusion length in thin silicon epitaxial layers was developed. Using a transparent MIS structure the surface recombination velocity was reduced below 25 cm/s. This method makes possible to determine minority carrier lifetime and also diffusion length much greater than the thickness of the epitaxial layer.     

Deep-level transient spectroscopy measurements using high Schottky barriers

This paper describes a method to investigate minority-carrier traps in semiconductors by utilizing high Schottky barrier diodes in DLTS (deep-level transient spectroscopy) measurements.

This offers an advantage compared to using pn diodes in that no excessive heat treatment which can alter the semiconductor deep-level properties has to be performed.

One of the best-known deep-level systems is the gold levels in silicon. The method is demonstrated for the gold donor level in n-type silicon by using iridium as Schottky contact.     

Specific features of the field generation of minority charge carriers in Si-SiO2 structures

The specific features of generation processes occurring in Si-SiO₂ structures in the presence of a strong electric field in the oxide layer (E _ox ≈ 10 MV cm^?1) are considered. It is shown that, after a certain threshold electric-field strength is reached, an additional mechanism of minority charge-carrier generation, associated with the development of electroluminescence processes in the oxide layer, becomes operative.     

Voltage measurement in GaAs Schottky barriers using optical phasemodulation

What are thought to be the first measurements of applied voltage in a GaAs Schottky-barrier diode using optical phase modulation are presented. A theoretical model, based on the refractive-index perturbation in a Schottky-barrier depletion region, describing these measurements was derived and gives good agreement with the observe results. The large signal response and large frequency response of the measurement system are illustrated. This technique facilitates high-sensitivity measurements of voltages in integrated Schottky diodes     

On the width of Schottky barriers

The paper presents numerical computations of the Schottky barrier width, made by taking the free carrier space charge into account, and points to substantial discrepancies between the actual and conventionally assumed volume as a function of current.     

Modification of GaAs Schottky barriers using a-Si:H interfaciallayers

The electrical characteristics of metal/a-Si:H/n-GaAs diode structures were studied in order to investigate the role of the a-Si:H and the claim of no barrier at the GaAs/a-Si:H interface. Diodes were fabricated using a-Si:H layers between 30 and 1920 Å thick, with Al and Mg metallization, and the current-voltage and capacitance-voltage characteristics were examined. Rectifying Schottky barriers were formed at Al/a-Si:H junctions, while good ohmic contacts were formed at Mg/a-Si:H junctions, enabling effects due to the metal/a-Si:H and a-Si:H/GaAs interface to be isolated. A dramatic increase in the forward turn-on voltage was observed as the thickness of the a-Si:H layer increased. The diode behavior can be explained by considering three effects in series: (1) an a-Si:H/GaAs barrier of about 0.6 eV, consistent with Fermi-level pinning in GaAs; (2) a metal/a-Si:H barrier, dependent on the metallization; and (3) space-charge-limited current (SCLC) in the bulk a-Si:H. The SCLC effectively gives rise to a voltage-dependent resistance and causes the increased turn-on voltages     

SB-IGFET, II: An ion implanted IGFET using Schottky barriers

Insulated-gate field-effect transistors have been made, which combine the advantages inherent to Schottky barrier source and drain electrodes with ion implantation. This device has a self-aligned gate structure achieved by using the thick gate electrode as a mask during the ion implantation process.     

Generation of minority charge carriers at the semiconductor surface during thermally activated ionic depolarization of metal-insulator-semiconductor structures

Relaxation signals represented by the temperature dependences of current J(T) and high-frequency capacitance C(T) and generated in the course of the thermally stimulated depolarization of a metal-insulator-semiconductor structure were analyzed numerically. Both the depletion of ionic traps located at the insulator-semiconductor interface and the generation of minority charge carriers from a bulk center with the activation energy _{E D} were taken into account.     

Analysis of minority carrier diffusion length in SiC toward high quality epitaxial growth

Homoepitaxy of 4H-SiC grown by a horizontal hot-wall chemical vapor deposition and the minority carrier diffusion length were studied. With the addition of HCl during the etching and the epitaxy, an optimum growth window on the C face became wide. Minority carrier diffusion length in SiC epilayers was evaluated by a line-scanning electron-beam-induced current method.     

Measurement of the mobility and concentration of charge carriers in a Gunn gallium-arsenide diode using a near-field microwave microscope

The results of local contactless measurement of the dependence of conductivity in a Gunn diode on the external electrical bias are presented. The technique of local determination of the charge-carrier concentration and mobility in a commercially produced chip Gunn diode for various values of the supply voltage is proposed.     

Formation of the nickel-platinum alloy silicide Schottky barriers

We propose a new technique for the Schottky barrier formation that involves magnetron deposition of a thin film from a multicomponent target consisting of vanadium, platinum, and nickel onto silicon and the subsequent stage thermal treatment. Using the developed technique, we fabricated device structures with the 0.69–0.71-V-high Schottky barriers. It is established that the barrier layer comprises the Ni_{1 ? x} Pt _x Si silicide phase and about 2 at % of platinum in the contact region. We show that the amount of platinum at the interface with silicon determines the barrier’s height. The highest platinum content at the interface is ensured at the two-stage thermal treatment at a first stage temperature of 240–300°C. The use of the two-stage thermal treatment in the silicide formation in the system’s silicon-composite Ni-Pt-V alloy allows obtaining a silicide layer with higher structural quality and a better silicon/silicide interface than the one-stage treatment can yield.     

Infrared optoelectronic properties of metal-germanium Schottky barriers

An experimental study has been made of the electronic properties of rectifying metal-Ge (n-type) contacts for a range of metals (Au, Cu, Ag, Pb, and Ni) and their optoelectronic characteristics under monochromatic illumination for λ = 0.6328 µm and for 1 µm < λ ≲ 2 µm in the near infrared. For each metal, very idealI-Vcharacteristics were obtained withnvalues from the exponential forward bias region of 1.02 to 1.08 and excellent reverse saturation at 300 K. The dependence of photoresponse on thickness of various metal electrodes (from 50 to more than 1000 Å) was observed.phi_{B}'sfound fromIV C-V, and photoresponse measurements are in close agreement within ±0.03 eV. The dependence of quantum efficiency (QE) upon metal thickness was measured for all metals and these results exhibit the expected decline in QE withd gsim 100Å. Ford lsim 100Å, QE can be as high as 75 percent at λ = 6328 Å, and 48 percent in the wavelength range 1.1 µm < λ < 1.4 µm. QE versushv(1 µm < λ < 2 µm) measurements have identified thresholds for the indirect and direct band-to-band excitation in the germanium and for the internal photoemission of electrons from the metal over the Schottky barrier induced by absorption of the infrared photons.     

Numerical evaluation of the scanning method for the determination of minority carrier diffusion length in p-n junctions

A numerical model for the scanning method for determining minority carrier diffusion length is presented to include the effect of the built-in field and high-level injection. A numerical simulation is presented which shows that the scanning method for diffusion length measurements will not give accurate results for minority carrier diffusion length in the region where the presence of a built-in field is significant. No matter how poor the junction is made, the accuracy of the measurement method increases away from the depletion region. The problem of low magnitude in the induced short circuit current away from the physical junction could be overcome by increasing the generation level. For substrate dopant concentrations between 2.0 × 10¹⁵cm⁻³ and 6.0 × 10¹⁶cm⁻³ the distance into the device from the surface where the error of the measurement will be greater than 10% is expressed as a semi-empirical formula relating dopant concentration. When there are irregularities in minority carrier lifetime closer to the physical junction, the measurement method will accurately determine the minority carrier diffusion length in a particular region only if the width of that region is much larger than its diffusion length.