No abstract

Electron detection at low energy range for scanning electron microscope (SEM), electron capture detector and electron probe micro-analysis (EPMA) applications, require detectors with high sensitivity and accuracy for low energy range. Such detectors must therefore have a thin entrance window and low recombination at the Si-SiO 2 interface. An electron detector with 100% photons to electron-hole pair production rate having a 10 nm SiO 2 passivating layer reveals a responsivity of approximately 0.25 A/W when irradiated. Simulations results showing the responsivity of electron interaction between detectors of varied interface fixed oxide charge density Q f show that there is an appreciable difference with the responsivity of a p + n detector and that of an n + p. The simulation results also show the significance of the effect of the minority carriers transport velocity S n,p on the responsivity of the detector.

Silicon detectors made on p-substrates are expected to have a better radiation hardness as compared to detectors made on n-substrates. However, the fixed positive oxide charges induce an inversion layer of electrons in the substrate, which connects the pixels. The common means of solving this problem is by using a p-spray, individual p-stops or a combination of the two. Here, we investigate the use of field plates to suppress the fixed positive charges and to prevent the formation of an inversion layer. The fabricated detector shows a high breakdown voltage and low interpixel leakage current for a structure using biased field plates with a width of 20 µm. By using a spice model for simulation of the preamplifier, a cross talk of about 1.6% is achieved with this detector structure. The cross talk is caused by capacitive and resistive coupling between the pixels.

This paper explores an alternative to the standard method of studying the responsivities (the input-output gain) and other behaviours of detectors at low electron energy. The research does not aim to compare the results of differently doped n C p detectors; its purpose is to provide an alternative characterization method (using scanning electron microscopy) to those used in previous studies on the responsivity of n C p doped detectors as a function of the electron radiation energy and other interface parameters.

Characterising a position sensitive detector in a vacuum environment without beam position monitoring devices can be challenging and expensive. With this in mind, the authors have designed and fabricated a duo-lateral position sensitive detector (PSD) incorporated with simple and inexpensive surface features. It was evaluated using scanning electron microscopy. To assist in pinpointing precise positioning as well as acting as path guide during the sweeping of electrons, multiple grids were lithographically patterned on the top layer of the duo-lateral PSD. By sweeping electrons along two axes of the detector, the position detection error of both axes was determined from the signals recorded using a transimpedance amplification circuit. They were able to characterise the linearity over the x-and y-axis of the PSD and the results show a very high linearity over two-dimensions of the PSD's active area and that accurate beam monitoring for spectroscopic measurement without additional beam position monitoring devices is possible.

No abstract

Lateral position sensitive devices (PSD) are important for triangulation, alignment and surface measurements as well as for angle measurements. Large PSDs show a delay on rising and falling edges when irradiated with near infra-red light [1]. This delay is also dependent on the spot position relative to the electrodes. It is however desirable in most applications to have a fast response. We investigated the responsiveness of a Sitek PSD in a mixed mode simulation of a two dimensional full sized detector. For simulation and measurement purposes focused light pulses with a wavelength of 850 nm, duration of 1 µs and spot size of 280 µm were used. The cause for the slopes of rise and fall time is due to time constants of the device capacitance as well as the photogeneration mechanism itself [1]. To support the simulated results, we conducted measurements of rise and fall times on a physical device. Additionally, we quantified the homogeneity of the device by repositioning a spot of light from a pulsed ir-laser diode on the surface area.

Surface states and interface recombination velocity that exist between detector interfaces have always been known to affect the performance of a detector. This article describes how the detector performance varies when the doping profile is altered. When irradiated with electrons, the results show that while changes in the doping profile have an effect of the detector responsivity with respect to the interface recombination velocity v s , there is no visible effect with respect to fixed oxide charge Q f otherwise known as interface fixed charge density.