| 摘要 |
PURPOSE:To obtain a semiconductor photo detector having preferable element characteristics by limiting electron density of N-type InP crystal when introducing Mg as P-type impurity to the N-type InP crystal, thereby simultaneously forming the photo detector and a guard ring. CONSTITUTION:An N-type InP crystal layer 12 having, for example, 2X10<15>cm<-3> of electron density is formed by a liquid-phase growing method on the main surface of an N-type InP substrate crystal 11. Then, a second InP crystal layer 13 is formed by a liquid-phase growing method to bury the etch-removed portion and an X' region to become an inner photo detector. The electron density of the layer 13 is so controlled as to become, for example 6X10<15>cm<-3>. Then, SiO2 and photoresist are selectively formed on the main surface of the InP crystals, and Mg ions are implanted. As a result, the carrier density of the layer 12 is set to 1X10<16>cm-3 or more and 1X10<17>cm<-3> or less of no adverse influence on noise characteristic, a stair type P-N junction photo detector is formed, and the carrier density of the layer 13 is set to 1X10<15>-1X10<16>cm<-3> to form a guard ring.
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