Methods of fabricating semiconductor structures and devices using quantum dot structures and related structures
Methods of fabricating photovoltaic devices include forming a plurality of subcells in a vertically stacked arrangement on a semiconductor material, each of the subcells being formed at a different temperature than an adjacent subcell such that the adjacent subcells have differing effective band-gaps. The methods of fabricating also include inverting the structure, attaching another substrate to a second semiconductor material, and removing the substrate. For example, each of the subcells may comprise a III-nitride material, and each subsequent subcell may include an indium content different than the adjacent subcell. Novel structures may be formed using such methods.
1. A method of forming a photovoltaic device, comprising:
forming a semiconductor structure or device, comprising:
depositing at least one layer of semiconductor material over a base substrate;
forming a subcell comprising one or more absorbance structures, wherein forming each of the one or more absorbance structures comprises:
disposing a plurality of quantum dots comprising indium gallium nitride to overlie at least a portion of the at least one layer of semiconductor material; and
depositing a barrier material comprising indium gallium nitride at a first temperature, the barrier material overlying and at least partially surrounding at least a portion of the plurality of quantum dots; and
after forming the subcell, forming at least another subcell over the subcell, the at least another subcell comprising one or more absorbance structures, wherein forming each of the one or more absorbance structures comprises:
disposing a plurality of quantum dots comprising indium gallium nitride to overlie at least a portion of the barrier material; and
depositing another barrier material comprising indium gallium nitride at a second temperature, the second temperature being less than the first temperature used to deposit the barrier material such that the at least another subcell has a substantially higher indium content than an underlying subcell, the another barrier material overlying and at least partially surrounding at least a portion of the plurality of quantum dots;
inverting the semiconductor structure or device;
bonding a carrier substrate to the semiconductor structure or device, wherein the carrier substrate is bonded to a surface of the semiconductor structure or device proximate to the another subcell; and
removing the base substrate.
2. The method of claim 1 , wherein depositing the barrier material comprising indium gallium nitride over and at least partially surrounding the plurality of quantum dots comprises depositing the barrier material such that the barrier material has a substantially lower indium content than an indium content of the plurality of quantum dots.
3. The method of claim 2 , wherein depositing the barrier material having a substantially lower indium content than an indium content of the plurality of quantum dots comprises depositing the barrier material at a temperature of greater than a growth temperature of the plurality of quantum dots.
4. The method of claim 1 , wherein forming at least another subcell comprising one or more absorbance structures comprises forming at least another absorbance structure having a substantially lower effective band-gap than the underlying subcell.
5. The method of claim 1 , wherein disposing a plurality of quantum dots comprising indium gallium nitride to overlie at least a portion of the barrier material comprises growing the plurality of quantum dots on an intermediate layer disposed on the barrier material.
6. The method of claim 1 , wherein disposing a plurality of quantum dots comprising indium gallium nitride to overlie at least a portion of the barrier material comprises growing the plurality of quantum dots directly on the barrier material.