Semiconductor photodetector using avalanche multiplication and strained layers

A semiconductor photodetector comprising at least a light absorptive layer and a superlattice avalanche multiplier layer on a semiconductor substrate, electrons generated at said light absorptive layer being injected to said superlattice avalanche multiplier layer under reverse bias, said superlattice avalanche multiplier layer comprising a first semiconductor layer and a second semiconductor layer, said first semiconductor layer having a lattice structure which matches the lattice of the substrate to provide a minimal strain, and wherein EA>EC and EB<ED where the mean ionizing energies of group III atoms and group V atoms of said first semiconductor layer are EA and EB, respectively, and the mean ionizing energies of group III atoms and group V atoms of said second semiconductor layer are EC and ED, respectively,

• a discontinuity of energy of the lower end of a conduction band being present at all the boundaries of said first and second semiconductor layers, first values of said discontinuity for all the boundaries being substantially equal, and
• the first semiconductor layer having substantially no strain and the second semiconductor layer having a tensile strain so that an effective mass of a hole within said second semiconductor layer, which travels in a direction of layer thickness, is made lighter and the difference between the energies at the lower end of the conduction band of said first and second semiconductor layers is made greater than an effective mass of a hole and of corresponding energies in a material identical in composition to said second semiconductor layer when under no strain.

A semiconductor photodetector comprising at least a light absorptive layer and a superlattice avalanche multiplier layer on a semiconductor substrate, electrons generated at said light absorptive layer being injected to said superlattice avalanche multiplier layer under reverse bias, said superlattice avalanche multiplier layer comprising a first semiconductor layer and a second semiconductor layer, said first layer having a lattice structure which matches the lattice structure of the substrate to produce a minimal strain, and wherein EA>EC and EB<ED where the mean ionizing energies of group III atoms and group V atoms of said first semiconductor layer are EA and EB, respectively, and the mean ionizing energies of group III atoms and group V atoms of said second semiconductor layer are EC and ED, respectively,

• a discontinuity of energy of the lower end of a conduction band being present at all the boundaries of said first and second semiconductor layers, first values of said discontinuity for all the boundaries being substantially equal, and
• the first semiconductor layer having no strain and the second semiconductor layer having a compressive strain so that the difference between the energies at the upper end of the valence band of said first and second semiconductor layers is made smaller than corresponding energies in a material identical in composition to said second semiconductor layer when under strain.

A semiconductor photodetector comprising at least a light absorptive layer and a superlattice avalanche multiplier layer on a semiconductor substrate, electrons generated at said light absorptive layer being injected to said superlattice avalanche multiplier layer under reverse bias, said superlattice avalanche multiplier layer comprising a first semiconductor layer and a second semiconductor layer, said second layer having a lattice structure which matches the lattice structures of the substrate to produce minimal strain, and wherein EA>EC and EB<Ed where the mean ionizing energies of group III atoms and group V atoms of said first semiconductor layer are EA and EB, respectively, and the mean ionizing energies of group III atoms and group V atoms of said second semiconductor layer are EC and ED, respectively,

• a discontinuity of energy of the lower end of a conduction band being present at all the boundaries of said first and second semiconductor layers, first values of said discontinuity for all the boundaries being substantially equal, and
• the first semiconductor layer having a tensile strain and the second semiconductor layer having a compressive strain so that an effective mass of a hole within said first semiconductor layer which travels in a direction of layer thickness is made lighter and the difference between the energies at the upper end of the valence band of said first and second semiconductor layers is made smaller than an effective mass of a hole in a material identical in composition to said first and second semiconductor layers when under no strain.

A semiconductor photodetector comprising at least a light absorptive layer and a superlattice avalanche multiplier layer on a semiconductor substrate, electrons generated at said light absorptive layer being injected to said superlattice avalanche multiplier layer under reverse bias, said superlattice avalanche multiplier comprising a first semiconductor layer and a second semiconductor layer, said second layer having a lattice structure which matches the lattice structure of the substrate to provide a minimum strain, and wherein EA>EC and EB<ED where the mean ionizing energies of group III atoms and group V atoms of said first semiconductor layer are EA and EB, respectively, and the mean ionizing energies of group III atoms and group V atoms of said second semiconductor layer are EC and ED, respectively,

• a discontinuity of energy of the lower end of a conduction band being present at all the boundaries of said first and second semiconductor layers, first values of said discontinuity for all the boundaries being substantially equal, and
• the first semiconductor layer having a tensile strain and the second semiconductor layer having a tensile strain so that an effective mass of a hole within said first and second semiconductor layer which travels in a direction of layer thickness is made lighter and the difference between the energies at the lower end of the conduction band of said first and second semiconductor layers is made greater than an effective mass of a hole in and of corresponding energies of a material identical in composition to said first and second semiconductor layers when under no strain.