Systems and methods for signal electron detection

An electron detector for detecting a plurality of signal electrons generated from a sample, comprising:

• a first semiconductor layer having a first portion and a second portion;
• a second semiconductor layer adjacent to the first semiconductor layer;
• a third semiconductor layer adjacent to the second semiconductor layer;
• a PIN region formed by the first, second, and third semiconductor layers;
• a power supply configured to apply a reverse bias between the first and the third semiconductor layers;
• and
• a depletion region formed within the PIN region by the reverse bias, the depletion region comprising a portion of the second semiconductor layer, and the depletion region configured to generate a detector signal based on a first subset of the plurality of signal electrons captured within the depletion region,
• wherein the second portion of the first semiconductor layer is not depleted and is configured to provide an energy barrier to block a second subset of the plurality of signal electrons and to allow the first subset of the plurality of signal electrons to pass through to reach the depletion region.