Method of producing a direct band gap in indirect band gap materials and light emitting or detecting devices fabricated therefrom
A method for creating direct band gap material from indirect band gap material, the resultant direct band gap material, and corresponding optical devices are described. The method employs atomic layer doping (ALDo) to create closely spaced δ-doped layers, alternating between n-type and p-type dopants, to modify the band structure of the indirect band gap material. The spacing between adjacent δ-doped layers is between 1 and 100 Å. The dopants may, for example, include phosphorus, boron, and/or aluminum, while the indirect band gap material may, for example, include silicon and/or germanium. The method and material may alternatively employ a single dopant for all closely spaced δ-doped layers. This single dopant may, for example, be erbium. Optical devices, including emitters and photodetectors, may be formed of the created direct band gap material. Both vertical and lateral devices may be formed.
1 . A device, comprising:
a layer of a first material;
a first doped layer comprising a first dopant type, the first doped layer adjacent the layer of the first material;
an interlayer of an indirect band gap material, the interlayer adjacent the first doped layer;
a second doped layer comprising a second dopant type, the second doped layer adjacent the interlayer, the second doped layer being a δ-doped layer;
a first electrical contact in contact with the first doped layer; and
a second electrical contact in contact with the second doped layer;
wherein a separation between the first doped layer and the second doped layer is adapted to modify a band structure of the interlayer such that at least a portion of the interlayer becomes a direct band gap material.
2 . The device of claim 1 , wherein:
the first doped layer is adjacent a first portion of the layer of the first material;
the second doped layer is adjacent a second portion of the layer of the first material; and
the second doped layer is laterally separated from the first doped layer by a distance.
3 . The device of claim 1 , wherein the interlayer is located between the first and second doped layers, thereby vertically separating the first doped layer from the second doped layer.
4 . The device of claim 1 , wherein both the first and second doped layers are δ-doped layers.
5 . The device of claim 1 , wherein the indirect band gap material includes one or more of carbon, germanium, silicon, or germanium tin.
6 . The device of claim 1 , wherein the separation is between 1 and 100 Å.
7 . The device of claim 1 , wherein:
each of the first dopant type and the second dopant type is one of an n-type dopant or a p-type dopant; and
each of the n-type or p-type dopants includes at least one of aluminum, antimony, arsenic, bismuth, boron, gallium, indium, nitrogen, or phosphorus.
8 . The device of claim 1 , further comprising:
a second interlayer of a second indirect band gap material, the second interlayer adjacent the second doped layer;
a third doped layer comprising the second dopant type, the third doped layer adjacent the second interlayer, the third doped layer being a δ-doped layer;
a third interlayer of a third indirect band gap material, the third interlayer adjacent the third doped layer; and
a fourth doped layer comprising the second dopant type, the fourth doped layer adjacent the third interlayer, the fourth doped layer being a δ-doped layer;
wherein thicknesses of the second and third interlayers are adapted to modify a corresponding band structure of each of the second and third interlayers such that a corresponding portion of each of the second and third interlayers becomes a corresponding direct band gap semiconductor material.
9 . The device of claim 1 , further comprising a third doped layer comprising a third dopant type, the third doped layer located within the interlayer, the third doped layer being a δ-doped layer.
10 . The device of claim 9 , wherein the third dopant type includes erbium or other rare earth element.
11 . The device of claim 1 , further comprising a third doped layer comprising a third dopant type, the third doped layer located adjacent a third portion of the layer of the first material, the third doped layer laterally separated from the first and second doped layers, the third doped layer being a δ-doped layer.
12 . The device of claim 11 , wherein the third dopant type includes erbium or other rare earth element.
13 . The device of claim 1 , further comprising:
a dielectric layer adjacent the second doped layer; and
a gate adjacent the dielectric layer, the gate adapted to receive a bias and to thereby create a field in the interlayer.
14 . The device of claim 1 , wherein the device is adapted to implement a function of an optical emitter or a photodetector.
15 . A device, comprising:
a layer of a first material;
a first doped layer comprising a first dopant type, the first doped layer adjacent the layer of the first material, the first doped layer being a δ-doped layer; and
an interlayer of an indirect band gap material, the interlayer adjacent the first doped layer;
wherein the first doped layer is adapted to modify a band structure of the interlayer such that at least a portion of the interlayer becomes a direct band gap material.
16 . The device of claim 15 , wherein the first dopant type includes erbium or other rare earth element.
17 . The device of claim 15 , wherein:
the first dopant type is one of an n-type dopant or a p-type dopant; and
the one of the n-type or p-type dopant includes at least one of aluminum, antimony, arsenic, bismuth, boron, gallium, indium, nitrogen, or phosphorus.
18 . The device of claim 17 , further comprising:
a dielectric layer adjacent the interlayer; and
a gate adjacent the dielectric layer, the gate adapted to receive a bias and to thereby create a gate induced carrier layer in the interlayer.
19 . The device of claim 15 , wherein the indirect band gap material includes one or more of carbon, germanium, silicon, or germanium tin.
20 . The device of claim 15 , wherein the device is adapted to implement a function of an optical emitter or a photodetector.