Light receiving/emitting element, solar cell, optical sensor, light emitting diode, and surface emitting laser element technical field

Abstract

A light receiving/emitting element 11 includes: a light receiving/emitting layer 21 in which a plurality of compound semiconductor layers are stacked; and an electrode 30 having a first surface 30 A and a second surface 30 B and made of a transparent conductive material, in which the second surface faces the first surface 30 A, and the electrode is in contact, at the first surface 30 A, with the light receiving/emitting layer 21 . The transparent conductive material contains an additive made of one or more metals, or a compound thereof, selected from the group consisting of molybdenum, tungsten, chromium, ruthenium, titanium, nickel, zinc, iron, and copper, and concentration of the additive contained in the transparent conductive material near an interface to the first surface 30 A of the electrode 30 is higher than concentration of the additive contained in the transparent conductive material near the second surface 30 B of the electrode 30.

1 . A light receiving/emitting element, comprising:
 a light receiving/emitting layer in which a plurality of compound semiconductor layers are stacked; and   an electrode having a first surface and a second surface and made of a transparent conductive material, the second surface facing the first surface, and the electrode being in contact, at the first surface, with the light receiving/emitting layer,   wherein the transparent conductive material contains an additive made of one or more metals, or a compound thereof, selected from the group consisting of molybdenum, tungsten, chromium, ruthenium, titanium, nickel, zinc, iron, and copper, and   concentration of the additive contained in the transparent conductive material near an interface to the first surface of the electrode is higher than concentration of the additive contained in the transparent conductive material near the second surface of the electrode.   
     
     
         2 . The light receiving/emitting element according to  claim 1 , wherein the compound semiconductor layers are each configured of one of: a GaAs-based compound semiconductor including binary mixed crystal, ternary mixed crystal, or quaternary mixed crystal; a GaP-based compound semiconductor including binary mixed crystal, ternary mixed crystal, or quaternary mixed crystal; a GaInP-based compound semiconductor including ternary mixed crystal or quaternary mixed crystal; an InP-based compound semiconductor including binary mixed crystal, ternary mixed crystal, or quaternary mixed crystal; and a GaN-based compound semiconductor including binary mixed crystal, ternary mixed crystal, or quaternary mixed crystal. 
     
     
         3 . The light receiving/emitting element according to  claim 1 , wherein the transparent conductive material is one of ITO, IZO, AZO, GZO, AlMgZnO, IGO, IGZO, IFO, ATO, FTO, SnO 2 , ZnO, B-doped ZnO, InSnZnO, and ITiO. 
     
     
         4 . The light receiving/emitting element according to  claim 1 , wherein auxiliary electrodes are formed on the second surface of the electrode. 
     
     
         5 . The light receiving/emitting element according to  claim 4 , wherein
 a contact layer is formed between the light receiving/emitting layer and the second surface of the electrode, and   the contact layer is configured of a compound semiconductor same as a compound semiconductor that configures one or more layers in the plurality of compound semiconductor layers configuring the light receiving/emitting layer.   
     
     
         6 . The light receiving/emitting element according to  claim 5 , wherein a thickness of the contact layer is from 3 nm to 30 nm where band gap energy of a material configuring the contact layer is smaller than band gap energy of the light receiving layer or the light emitting layer. 
     
     
         7 . The light receiving/emitting element according to  claim 1 , wherein
 the electrode has a stacked structure including a first layer and a second layer from light receiving/emitting layer side,   the additive is contained in the transparent conductive material configuring the first layer, and   no additive is contained in the transparent conductive material configuring the second layer.   
     
     
         8 . The light receiving/emitting element according to  claim 7 , wherein mean concentration of the additive contained in the transparent conductive material configuring the first layer is from 5×10 16  cm −3  to 1×10 18  cm −3 . 
     
     
         9 . The light receiving/emitting element according to  claim 7 , wherein the following expressions are satisfied:
   0.4≦ R   2   /R   1 ≦1.0
     0.8≦ TP   2   ×TP   1 ≦1.0
   where electrical resistivity of the first layer is R 1 , electrical resistivity of the second layer is R 2 , and light transmittance of the first layer and light transmittance of the second layer are TP 1  and TP 2 , respectively, where a wavelength ranges from 400 nm to 900 nm.   
     
     
         10 . The light receiving/emitting element according to  claim 1 , wherein concentration of the additive contained in the transparent conductive material configuring the electrode decreases gradually from the first surface to the second surface of the electrode. 
     
     
         11 . A solar cell, comprising:
 a light receiving layer in which a plurality of compound semiconductor layers are stacked; and   an electrode having a first surface and a second surface and made of a transparent conductive material, the second surface facing the first surface, and the electrode being in contact, at the first surface, with the light receiving layer,   wherein the transparent conductive material contains an additive made of one or more metals, or a compound thereof, selected from the group consisting of molybdenum, tungsten, chromium, ruthenium, titanium, nickel, zinc, iron, and copper, and   concentration of the additive contained in the transparent conductive material near an interface to the first surface of the electrode is higher than concentration of the additive contained in the transparent conductive material near the second surface of the electrode.   
     
     
         12 . The solar cell according to  claim 11 , wherein
 auxiliary electrodes are formed on the second surface of the electrode,   a contact layer is formed between the light-receiving layer and the first surface of the electrode, and   a reflection prevention film is formed on the exposed second surface of the electrode.   
     
     
         13 . The solar cell according to  claim 12 , wherein
 a width of a portion of the second surface of the electrode, exposed between the auxiliary electrodes, is from 145 μm to 285 μm,   a thickness of the electrode is from 10 nm to 30 nm, and   the reflection prevention film has a stacked structure including a zinc sulfide layer having a thickness from 17 nm to 36 nm and a magnesium fluoride layer having a thickness from 85 nm to 93 nm.   
     
     
         14 . The solar cell according to  claim 12 , wherein
 a width of a portion of the second surface of the electrode, exposed between the auxiliary electrodes, is from 145 μm to 285 μm,   a thickness of the electrode is from 10 nm to 30 nm, and   the reflection prevention film has a stacked structure including a tantalum oxide layer having a thickness from 18 nm to 32 nm and a silicon oxide layer having a thickness from 71 nm to 76 nm.   
     
     
         15 . The solar cell according to  claim 12 , wherein
 a width of a portion of the second surface of the electrode, exposed between the auxiliary electrodes, is from 145 μm to 285 μm,   a thickness of the electrode is from 10 nm to 25 nm, and   the reflection prevention film has a stacked structure including a titanium oxide layer having a thickness from 7 nm to 15 nm, a tantalum oxide layer having a thickness from 14 nm to 34 nm, and a silicon oxide layer having a thickness from 81 nm to 86 nm.   
     
     
         16 . The solar cell according to  claim 11 , wherein
 auxiliary electrodes are formed on the second surface of the electrode,   a contact layer is formed between the light-receiving layer and the first surface of the electrode, and   a portion of the second surface of the electrode, exposed between the auxiliary electrodes, is provided with recesses and projections.   
     
     
         17 . An optical sensor, comprising:
 a light receiving layer in which a plurality of compound semiconductor layers are stacked; and   an electrode having a first surface and a second surface and made of a transparent conductive material, the second surface facing the first surface, and the electrode being in contact, at the first surface, with the light receiving layer,   wherein the transparent conductive material contains an additive made of one or more metals, or a compound thereof, selected from the group consisting of molybdenum, tungsten, chromium, ruthenium, titanium, nickel, zinc, iron, and copper, and   concentration of the additive contained in the transparent conductive material near an interface to the first surface of the electrode is higher than concentration of the additive contained in the transparent conductive material near the second surface of the electrode.   
     
     
         18 . A light emitting diode, comprising:
 a light emitting layer in which a plurality of compound semiconductor layers are stacked; and   an electrode having a first surface and a second surface and made of a transparent conductive material, the second surface facing the first surface, and the electrode being in contact, at the first surface, with the light emitting layer,   wherein the transparent conductive material contains an additive made of one or more metals, or a compound thereof, selected from the group consisting of molybdenum, tungsten, chromium, ruthenium, titanium, nickel, zinc, iron, and copper, and   concentration of the additive contained in the transparent conductive material near an interface to the first surface of the electrode is higher than concentration of the additive contained in the transparent conductive material near the second surface of the electrode.   
     
     
         19 . A surface emitting laser element, comprising:
 a light emitting layer in which a plurality of compound semiconductor layers are stacked; and   an electrode having a first surface and a second surface and made of a transparent conductive material, the second surface facing the first surface, and the electrode being in contact, at the first surface, with the light emitting layer,   wherein the transparent conductive material contains an additive made of one or more metals, or a compound thereof, selected from the group consisting of molybdenum, tungsten, chromium, ruthenium, titanium, nickel, zinc, iron, and copper, and   concentration of the additive contained in the transparent conductive material near an interface to the first surface of the electrode is higher than concentration of the additive contained in the transparent conductive material near the second surface of the electrode.