Staggered composition quantum well method and device
A light emitting device comprising a staggered composition quantum well (QW) has a step-function-like profile in the QW, which provides higher radiative efficiency and optical gain by providing improved electron-hole wavefunction overlap. The staggered QW includes adjacent layers having distinctly different compositions. The staggered QW has adjacent layers X n wherein X is a quantum well component and in one quantum well layer n is a material composition selected for emission at a first target light regime, and in at least one other quantum well layer n is a distinctly different composition for emission at a different target light regime. X may be an In-content layer and the multiple X n -containing a step function In-content profile.
1. A light emitting device comprising:
a staggered composition quantum well, said staggered composition quantum well comprising a type I quantum well comprising:
a pair of large band gap barrier layers; and
a quantum well active region sandwiched between said pair of large band gap barrier layers, said quantum well active region having a non-uniform material composition, said quantum well active region comprising a plurality of active layers, a first of said plurality of active layers having a first material composition, a second of said plurality of active layers having a second material composition distinctly different from said first material composition, said first and second material compositions collectively providing a step function in material composition within said quantum well active region.
2. The light emitting device of claim 1 , wherein said plurality of active layers comprises staggered GaN/InGaN layers.
3. The light emitting device of claim 1 , wherein the quantum well comprises multiple InGaN layers have complementary step function In-content profiles.
4. The light emitting device of claim 1 , wherein said plurality of active layers comprises multiple InGaN layers of varying In and Ga contents.
5. The light emitting device of claim 1 , wherein said plurality of active layers comprises multiple InGaN layers comprising 4-periods of 7.5-Å In 0.25 Ga 0.75 N/7.5-Å In 0.15 Ga 0.85 N.
6. The light emitting device of claim 1 , comprising a substrate; a first contact layer comprising a GaN-based material having a first conduction type located on top of the substrate; an active layer comprising the staggered composition quantum well located on top of the first contact layer; a second contact layer comprising a GaN-based material having a second conduction type opposite to the first conduction type located on top of the active layer.
7. The light emitting device of claim 1 , comprising a staggered 13-Å In 0.28 Ga 0.72 N/13-Å In 0.21 Ga 0.79 N QW emitting at λ peak =500-510 nm.
8. A light emitting device comprising a staggered composition quantum well wherein the quantum well active region comprises multiple InGaN active layers selected from the staggered layer combinations consisting of 7.5-Å In 0.25 Ga 0.75 N/7.5-Å In 0.15 Ga 0.85 N; 12-Å In 0.25 Ga 0.75 N/12-Å In 0.15 Ga 0.85 N; 13-Å In 0.28 Ga 0.72 N/13-Å In 0.21 Ga 0.79 N; and 4-periods of 7.5-Å In 0.25 Ga 0.75 N/7.5-Å In 1.15 Ga 0.85 N.
9. A method for improving radiative light efficiency of a light emitting device, comprising:
providing a semiconductor substrate; and
forming on the substrate, a succession of layers to provide quantum well active region surrounded by GaN barrier layers, said quantum well active region having a non-uniform material composition, said quantum well active region comprising a plurality of active layers, a first of said plurality of active layers having a first material composition, a second of said plurality of active layers having a second material composition distinctly different from said first material composition, said first and second material compositions collectively providing a step function in material composition within said quantum well active region.
10. The product of the process of claim 9 .
11. An optoelectronic device comprising:
a multilayer semiconductor structure comprising a GaN layer and an active region, the active region comprising a staggered composition quantum well, said staggered composition quantum well comprising a quantum well active region having a non-uniform material composition, said quantum well active region comprising a plurality of active layers, a first of said plurality of active layers having a first material composition, a second of said plurality of active layers having a second material composition distinctly different from said first material composition, said first and second material compositions collectively providing a step function in material composition within said quantum well active region.
12. The optoelectronic device of claim 11 , wherein the quantum well comprises staggered GaN/InGaN layers.
13. The optoelectronic device of claim 11 , wherein the quantum well comprises multiple InGaN layers have complementary step function In-content profiles.
14. The optoelectronic device of claim 11 , wherein the quantum well comprises multiple InGaN layers of varying In and Ga content.
15. The optoelectronic device of claim 11 , wherein the quantum well comprises multiple InGaN layers selected from the staggered layer combinations consisting of 7.5-Å In 0.25 Ga 0.75 N/7.5-Å In 0.15 Ga 0.85 N; 12-Å In 0.25 Ga 0.75 N/12-Å In 0.15 Ga 0.85 N; 13-Å In 0.28 Ga 0.72 N/13-Å In 0.21 Ga 0.79 N; and 4-periods of 7.5-Å In 0.25 Ga 0.75 N/7.5-Å In 0.15 Ga 0.85 N.
16. The optoelectronic device of claim 11 , wherein the quantum well comprises multiple InGaN layers comprising 4-periods of 7.5-Å In 0.25 Ga 0.75 N/7.5-Å In 0.15 Ga 0.85 N.
17. The optoelectronic device of claim 11 , comprising a substrate; a first contact layer comprising a GaN-based material having a first conduction type located on top of the substrate; an active layer comprising the staggered composition quantum well located on top of the first contact layer; a second contact layer comprising a GaN-based material having a second conduction type opposite to the first conduction type located on top of the active layer.
18. A method for generating optical emission from an optoelectronic device, comprising: providing a GaN layer and an active region, the active region comprising a staggered composition quantum well; and exciting the active region to produce optical emission.