Avalanche photodiodes having accurate and reproductible amplification layer

An avalanche photodiode comprising:

• a compound semiconductor absorption layer on an n-type substrate;
• a compound semiconductor grading layer on the compound semiconductor absorption layer;
• a charge sheet layer on the compound semiconductor grading layer;
• a compound semiconductor amplification layer on the charge sheet layer;
• a selective wet etch layer aperture pattern on the compound semiconductor amplification layer;
• a dielectric layer on the compound semiconductor amplification layer;
• and
• a p-type conductive mesa pattern on the selective wet etch layer aperture pattern,
• wherein:
• the aperture pattern has a side wall which comes in contact with the dielectric layer;
• and
• the aperture pattern has an upper surface that faces the p-type conductive mesa pattern, and the entire upper surface of the aperture pattern is covered by the p-type conductive mesa pattern.