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We report a versatile system for measuring excess noise and multiplication in avalanche photodiodes, using a transimpedance amplifier front-end and based on phase-sensitive detection, which permits accurate measurement in the presence of a high dark current. The system, which we have used successfully on a wide variety of materials and device structures, can measure reliably the excess noise factor of devices with a capacitance of up to ∼50 pF.

The avalanche multiplication and excess noise properties of a range of submicron Si diodes have been investigated. In these thin diodes the excess noise is found to fall below that predicted by conventional local noise theory. Modeling of the multiplication and excess noise using a recurrence method, which includes the dead space for carrier ionization, gives good agreement with experiment. This suggests that the dead space can reduce the excess noise in submicron Si diodes.

The impact ionization coefficients in bulk Al0.8Ga0.2As have been determined from photomultiplication measurements over the electric field range of 328–519 kV/cm. Unlike in AlxGa1−xAs (x⩽0.6), where the electron to hole ionization coefficients ratios (1/k) are less than 2, the 1/k value in Al0.8Ga0.2As was found to be greater than 10. Excess noise measurements corroborated the multiplication results, suggesting that this material may be a suitable multiplication medium for low noise avalanche photodiodes.

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ReuseUnless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. ) for hole (electron) injection, was measured with 365-nm light in both structures. Modeling the experimental results using a simple quantum efficiency model and a nonlocal description yields effective ionization threshold energies of 12 and 8 eV for electrons and holes, respectively, and suggests that the dead space in 4H-SiC is soft. Although dead space is important, pure hole injection is still required to ensure low excess noise in thin 4H-SiC APDs owing to ratios that remain large, even at very high fields.

The performance of Al 0.52 In 0.48 P avalanche photodiodes was assessed as soft X-ray detectors at room temperature. The effect of the avalanche gain improved the energy resolution and an energy resolution (FWHM) of 682 eV is reported for 5.9 keV X-rays.