A silicon drift photodiode

Abstract

A low capacitance photodiode based on the principle of the solid state drift chamber has been constructed and tested. The device is based on a cellular design with an anode at the centre of each of five cells allowing electrons liberated by ionisation to drift up to lmm to the read out strip. Results on the performance of the detector, including leakage current, capacitance and drift properties, are presented and compared with simulations.

Ultra-Low Capacitance Spot PIN Photodiodes

“…A very large silicon volume, which is very low doped, is depleted with the help of several electrodes and the device capacitance is practically that of the readout electrode only. An active area of 30 mm² was reported [26]. Starting from a readout N+ region of 50 µm times 8 mm and a capacitance of about 0.8 pF [26], 0.1 pF were reached for a light-sensitive area of 13 mm² [27].…”

“…Another class of low-capacitance photodetectors are silicon drift photodiodes for X-ray and gamma-ray spectroscopy [26][27][28]. A very large silicon volume, which is very low doped, is depleted with the help of several electrodes and the device capacitance is practically that of the readout electrode only.…”

<title>Low-temperature operation of silicon drift detectors</title>

“…8 Electrons drift from their point of production to the nearest anode. The potential distribution inside the detector is such that the drift paths are not parallel to the surface, nor is the field constant at all points along the drift path.…”

“…For these tests all the anodes were connected together to ensure complete charge collection despite uncertainties in the electron drift paths caused by material 12 The trigger signal was derived from the orthogonal cathode strips on the rear surface. These strips were also all connected together.…”

Evaluation of bismuth germanate detectors

“…This leads to larger photodiodes,that are noisier due to their larger capacitance,which in turn results in poorer resolution. One promisingavenue in this regard is the developmentof the drift silicon diodes (Avset et al 1989), which will have negligiblecapacitanceregardlessof size. Unfortunately,although work has been going on in this area for severalyears, progresshas been extremely slow.…”