Semiconductor device

Abstract

A semiconductor device includes a substrate, an initial layer, and a superlattice stack. The initial layer is located on the substrate and includes aluminum nitride (AlN). The superlattice stack is located on the initial layer and includes a plurality of first films and a plurality of second films, and the first films and the second films are alternately stacked on the initial layer. If the first films are doped films having dopants selected from a group consisting of carbon, iron, and the combination thereof, the second films do not include dopants substantially; if the second films are doped films having dopants selected from a group consisting of carbon, iron, and the combination thereof, the first films do not include dopants substantially.

What is claimed is: 
     
         1 . A semiconductor device comprising:
 a substrate;   an initial layer located on the substrate, the initial layer comprising aluminum nitride; and   a superlattice stack located on the initial layer, the superlattice stack comprising a plurality of first films and a plurality of second films, the first films and the second films being alternately stacked on the initial layer, wherein at least one of the first films and the second films is a doped layer having dopants selected from a group consisting of carbon, iron, and the combination thereof, and the other films do not comprise dopants substantially.   
     
     
         2 . The semiconductor device of  claim 1 , wherein the first films comprise Al x Ga 1-x N or aluminum nitride, the second films comprise Al y Ga 1-y N or gallium nitride, X and Y are between 0 and 1 and are neither equal to 0 nor equal to 1, and X is not equal to Y. 
     
     
         3 . The semiconductor device of  claim 1 , wherein the first films are the doped layers, and the second films do not comprise carbon or iron substantially. 
     
     
         4 . The semiconductor device of  claim 1 , wherein the second films are the doped layers, and the first films do not comprise carbon or iron substantially. 
     
     
         5 . The semiconductor device of  claim 1 , further comprising a buffer stack located between the superlattice stack and the initial layer. 
     
     
         6 . The semiconductor device of  claim 5 , wherein the buffer stack comprises a plurality of base layers and at least one doped layer positioned between two adjacent base layers, the base layers comprise aluminum gallium nitride, the at least one doped layer comprises aluminum gallium nitride or boron aluminum gallium nitride, in the buffer stack, concentrations of aluminum in the base layers gradually decrease, concentrations of gallium in the base layers gradually increase, dopants in the at least one doped layer comprise carbon or iron, and the base layers do not comprise carbon or iron substantially. 
     
     
         7 . The semiconductor device of  claim 6 , wherein the number of the at least one doped layer is plural, and the doped layers and the base layers are alternately stacked on the initial layer. 
     
     
         8 . The semiconductor device of  claim 1 , further comprising a plurality of buffer stacks located between the superlattice stack and the initial layer, at least one of the buffer stacks comprises a first base layer, a first doped layer, and a second base layer, a concentration of aluminum in the first base layer is substantially the same as a concentration of aluminum in the second base layer, the first doped layer is positioned between the first base layer and the second base layer, the first and second base layers comprise aluminum gallium nitride, the first doped layer comprises aluminum gallium nitride or boron aluminum gallium nitride, dopants in the first doped layer comprise carbon or iron, and the first and second base layers do not comprise carbon or iron substantially. 
     
     
         9 . The semiconductor device of  claim 8 , wherein each of the buffer stacks comprises a first doped layer positioned between the first base layer and the second base layer. 
     
     
         10 . The semiconductor device of  claim 8 , wherein the at least one of the buffer stacks further comprises a second doped layer and a third base layer, and the second doped layer is positioned between the second base layer and the third base layer. 
     
     
         11 . The semiconductor device of  claim 10 , wherein the second doped layer comprises aluminum gallium nitride or boron aluminum gallium nitride, and the third base layer does not comprise carbon or iron substantially. 
     
     
         12 . The semiconductor device of  claim 10 , wherein in each of the buffer stacks, concentrations of aluminum in the first base layer, the second base layer, and the third base layer are substantially the same. 
     
     
         13 . A semiconductor device comprising:
 a substrate;   an initial layer located on the substrate, the initial layer comprising aluminum nitride; and   a superlattice stack located on the initial layer, the superlattice stack comprising a plurality of first films, a plurality of second films, and at least one doped layer, the first films and the second films being alternately stacked on the initial layer, wherein the at least one doped layer is arranged in one of the first films and the second films, and dopants of the at least one doped layer are selected from a group consisting of carbon, iron, and the combination thereof.   
     
     
         14 . The semiconductor device of  claim 13 , wherein the first films comprise Al x Ga 1-x N or aluminum nitride, the second films comprise Al y Ga 1-y N or gallium nitride, X and Y are between 0 and 1 and are neither equal to 0 nor equal to 1, and X is not equal to Y. 
     
     
         15 . The semiconductor device of  claim 13 , wherein the at least one doped layer is located in the first films, and the second films do not comprise carbon or iron substantially. 
     
     
         16 . The semiconductor device of  claim 13 , wherein the at least one doped layer is located in the second films, and the first films do not comprise carbon or iron substantially. 
     
     
         17 . The semiconductor device of  claim 13 , wherein the at least one doped layer is located in the first films and the second films. 
     
     
         18 . The semiconductor device of  claim 13 , further comprising a buffer stack located between the superlattice stack and the initial layer. 
     
     
         19 . The semiconductor device of  claim 18 , wherein the buffer stack comprises a plurality of base layers and at least one doped layer positioned between two adjacent base layers, the base layers comprise aluminum gallium nitride, the at least one doped layer comprises aluminum gallium nitride or boron aluminum gallium nitride, in the buffer stack, concentrations of aluminum in the base layers gradually decrease, concentrations of gallium in the base layers gradually increase, dopants in the at least one doped layer comprise carbon or iron, and the base layers do not comprise carbon or iron substantially. 
     
     
         20 . The semiconductor device of  claim 18 , comprising a plurality of doped layers, and the doped layers and the base layers are alternately stacked on the initial layer. 
     
     
         21 . The semiconductor device of  claim 13 , further comprising a plurality of buffer stacks located between the superlattice stack and the initial layer, at least one of the buffer stacks comprises a first base layer, a first doped layer, and a second base layer, a concentration of aluminum in the first base layer is higher than a concentration of aluminum in the second base layer, the first doped layer is positioned between the first base layer and the second base layer, the first and second base layers comprise aluminum gallium nitride, the first doped layer comprises aluminum gallium nitride or boron aluminum gallium nitride, dopants in the first doped layer comprise carbon or iron, and the first and second base layers do not comprise carbon or iron substantially. 
     
     
         22 . The semiconductor device of  claim 21 , wherein each of the buffer stacks comprises the first doped layer positioned between the first base layer and the second base layer. 
     
     
         23 . The semiconductor device of  claim 21 , wherein the at least one of the buffer stacks further comprises a second doped layer and a third base layer, and the second doped layer is positioned between the second base layer and the third base layer. 
     
     
         24 . The semiconductor device of  claim 23 , wherein the second doped layer comprises aluminum gallium nitride or boron aluminum gallium nitride, and the third base layer does not comprise carbon or iron substantially. 
     
     
         25 . The semiconductor device of  claim 23 , wherein concentrations of aluminum in the first base layer, the second base layer, and the third base layer in each of the buffer stacks are substantially the same, and concentrations of aluminum in the buffer stacks gradually decrease from bottom to top.