Avalanche photodiode with hetero-periodical structure

Claim 1

An avalanche photodiode, comprising: a light absorbing layer; an avalanche multiplication layer of a hetero-periodical structure comprising alternately provided first barrier and well layers, each of said first barrier layers of said avalanche multiplication layer comprising a multi-quantum barrier layer having alternately provided narrow-width barrier and well layers, a virtual barrier being formed which is higher than said first barrier and is generated at the multi-quantum barrier layer, so that electrons which are injected into the avalanche multiplication layer experience large energy differences between the virtual barrier and the well layer so that electrons obtain a large ionizing energy; and first and second electrodes for applying a predetermined voltage across said light absorbing and avalanche multiplication layers; wherein said narrow-width barrier and well layers comprise respectively first and second group III-V compounds which meet the following conditions: E.sub.A <E.sub.B, and E.sub.A +E.sub.gA <E.sub.B +E.sub.gB where E A and E B are average ionization energies of said first and second group III-V compounds, respectively, and E gA and E gB are forbidden band gap energies, respectively.