Laser diode

Abstract

A laser diode with an improved kink level in the L-I characteristic and capable of obtaining a stable high output in a horizontal transverse mode is provided. The laser diode includes an active layer made of nitride III-V compound semiconductor containing at least gallium (Ga) in 3B-group elements and at least nitrogen (N) in 5B-group elements, an n-type compound semiconductor layer provided on one of faces of the active layer, and a p-type compound semiconductor layer provided on the other face of the active layer. A region closest to the active layer, in the n-type compound semiconductor layer is a high-concentration region whose impurity concentration is higher than that of the other n-type regions.

1 - 15 . (canceled) 
     
     
         16 . A laser diode comprising:
 a p-type compound semiconductor layer;   an n-type compound semiconductor layer that includes an n-type cladding layer and   an n-type guide layer; and   an active layer between the p-type compound semiconductor layer and the n-type compound semiconductor layer,   wherein a concentration of an n-type impurity in the n-type guide layer is at least three times as high as a concentration of an n-type impurity in the n-type cladding layer, and   wherein the concentration of the n-type impurity in the n-type guide layer is within a range from 3×10 18  cm −3  to 1×10 21  cm −3 .   
     
     
         17 . The laser diode according to  claim 16 , wherein the active layer is a compound semiconductor containing at least gallium (Ga) and nitrogen (N). 
     
     
         18 . The laser diode according to  claim 17 , wherein the active layer is made of In x Ga 1-x N (x>=0). 
     
     
         19 . The laser diode according to  claim 18 , wherein the active layer has a multiple quantum well structure of a well layer and a barrier layer made of In x Ga 1-x N (x>=0) of different compositions. 
     
     
         20 . The laser diode according to  claim 16 , wherein the n-type guide layer is between the active layer and the n-type cladding layer. 
     
     
         21 . The laser diode according to  claim 16 , wherein the n-type guide layer has a band gap narrower than a band gap of the n-type cladding layer. 
     
     
         22 . The laser diode according to  claim 16 , wherein the n-type guide layer has a refractive index higher than a refractive index of the n-type cladding layer. 
     
     
         23 . The laser diode according to  claim 16 , further comprising:
 an undoped i-type guide layer between the n-type guide layer and the active layer.   
     
     
         24 . The laser diode according to  claim 23 , wherein the undoped i-type guide layer is made of In x Ga 1-x N (x>=0). 
     
     
         25 . The laser diode according to  claim 16 , wherein the concentration of the n-type impurity in the n-type guide layer lies within a range from 5×10 18  cm −3  to 1×10 20  cm −3 . 
     
     
         26 . The laser diode according to  claim 16 , further comprising:
 a substrate made of n-type GaN.   
     
     
         27 . The laser diode according to  claim 16 , wherein the n-type impurity containing at least silicon (Si), oxygen (O), germanium (Ge), selenium (Se) or sulfur (S). 
     
     
         28 . The laser diode according to  claim 16 , wherein the n-type compound semiconductor layer includes a buffer layer. 
     
     
         29 . The laser diode according to  claim 28 , wherein the buffer layer is made of n-type GaN. 
     
     
         30 . The laser diode according to  claim 16 , wherein the p-type compound semiconductor layer includes an electronic barrier layer made of p-type AlGaN. 
     
     
         31 . The laser diode according to  claim 16 , wherein the p-type compound semiconductor layer includes p-type superlattice cladding layer in which a p-type AlGaN layer doped with magnesium (Mg).