Abstract: A single photon avalanche diode (SPAD) device is presented. The SPAD device comprising: a Si-based avalanche layer formed over an n-type semiconductor contact layer; a p-type charge sheet layer formed in or on the avalanche layer, the p-type charge sheet layer having an in-plane width; a Ge-based absorber layer, formed over the charge sheet layer and/or the avalanche layer, and overlapping the charge sheet layer, the Ge-based absorber layer having an in-plane width; wherein, at least in one in-plane direction, the in-plane width of the Ge-based absorber layer is greater than the in-plane width of the p-type charge sheet layer.

Abstract: An acceleration measuring device is disclosed, for use as a gravimeter or gradiometer for example. The device has a support and a proof mass, connected to each other by at flexures allowing displacement of the proof mass relative to the support. The support defines a space for displacement of the proof mass. The device is configured so that the modulus of the gradient of the force-displacement curve of the proof mass decreases with increasing displacement, for at least part of the force-displacement curve. This is the so-called anti-spring effect. The resonant frequency of oscillation of the proof mass is determined at least in part by the orientation of the device relative to the direction of the force due to gravity. The proof mass is capable of oscillating with a resonant frequency of 10 Hz or less. The proof mass has a mass of less than 1 gram.

Abstract: An acceleration measuring device is disclosed, for use as a gravimeter or gradiometer for example. The device has a support and a proof mass, connected to each other by at flexures allowing displacement of the proof mass relative to the support. The support defines a space for displacement of the proof mass. The device is configured so that the modulus of the gradient of the force-displacement curve of the proof mass decreases with increasing displacement, for at least part of the force-displacement curve. This is the so-called anti-spring effect. The resonant frequency of oscillation of the proof mass is determined at least in part by the orientation of the device relative to the direction of the force due to gravity. The proof mass is capable of oscillating with a resonant frequency of 10 Hz or less. The proof mass has a mass of less than 1 gram.