Patent ID: 7928472

Claim:
An optical semiconductor device comprising: a distributed Bragg reflector layer of a first conductivity type including at least one first semiconductor layer having a first physical thickness and formed from a first material having a first band gap wavelength, and at least one second semiconductor layer having a second physical thickness and formed from a second material having a second band gap wavelength; an optical absorption layer; and a semiconductor layer of a second conductivity type, sequentially formed on a semiconductor substrate, wherein a given incident vacuum wavelength is intermediate between the first and second band gap wavelength, at said incident vacuum wavelength, the first material has a first refractive index and the first semiconductor layer has a first optical layer thickness equal to the product of the first physical thickness multiplied by the first refractive index divided by the incident vacuum wavelength, at said incident vacuum wavelength, the second material has a second refractive index and the second semiconductor layer has a second optical layer thickness equal to the product of second physical thickness multiplied by the second refractive index divided by the incident vacuum wavelength, and the second band gap wavelength is larger than the first band gap wavelength, the second refractive index is higher than the first refractive index, and the first optical layer thickness is larger than the second optical layer thickness.