Strain-controlled atomic layer epitaxy, quantum wells and superlattices prepared thereby and uses thereof
View Patent ↗Processes for forming quantum well structures which are characterized by controllable nitride content are provided, as well as superlattice structures, optical devices and optical communication systems based thereon.
1. A process of forming a quantum well structure which comprises a base-layer, a well-layer which comprises a group-III element, a group-V element and nitrogen, and a cap-layer, the process comprising:
epitaxially growing the base-layer on a substrate;
epitaxially growing the well-layer on the base-layer; and
epitaxially growing the cap-layer on the well-layer,
thereby forming the quantum well structure,
wherein said epitaxially growing the well-layer comprises:
exposing the base-layer to a precursor of a group-III element, to thereby form on the base-layer a first atomic layer which comprises the group-III element deposited thereon;
terminating said exposing to said precursor of a group-III element;
exposing the base-layer having said first atomic layer to a precursor of nitrogen, to thereby form the base-layer having said first atomic layer deposited thereon and said nitrogen absorbed onto said first atomic later;
terminating said exposing to said precursor of nitrogen;
exposing the base-layer to a precursor of a group-III element, to thereby form on the base-layer a second atomic layer which comprises the group-III element;
terminating said exposing to said precursor of the group-III element; and
exposing the base-layer having said first atomic layer, said nitrogen and said second atomic layer deposited thereon, to a precursor of a group-V element, to thereby form the well-layer.
2. The process of claim 1 , wherein exposing said base layer, said base layer having said first atomic layer and said nitrogen, and said base layer having said first and/or said second atomic layers is effected so as to form said well-layer as a multi-monolayer well-layer.
3. The process of claim 1 , wherein said well-layer is a two-monolayer well-layer.
4. The process of claim 1 , wherein a number of atoms of the group-III element is at least 50 percent of the total number of atoms of the well-layer.
5. The process of claim 4 , wherein a number of nitrogen atoms ranges from 0.1 percent to 5 percents of the total number of atoms of the well-layer.
6. The process of claim 5 , wherein a strain in said first atomic layer is greater than 2%.
7. The process of claim 5 , wherein a strain in said first atomic layer is greater than 7%.
8. The process of claim 6 , wherein exposing the base-layer to said precursor of the group-III element is performed for a time period that ranges from 5 second to 50 seconds.
9. The process of claim 8 , wherein said time period ranges from 6 second to 10 seconds.
10. The process of claim 9 , wherein said time period is 7 seconds.
11. The process of claim 5 , wherein epitaxially growing the well-layer onto the base-layer in said reaction chamber is performed at a temperature not higher than 520° C.
12. The process of claim 1 , wherein each of the base-layer and the cap-layer independently comprises a substance selected from the group consisting of GaAs, GaAsSb, GaAsSbN, AlGaAs, GaAsP, GaInAs, GaSb and GaSbN.
13. The process of claim 1 , wherein epitaxially growing said cap-layer is performed at a temperature not higher than 520° C.
14. The process of claim 1 , further comprising, subsequent to epitaxially growing said cap-layer, epitaxially growing an additional well-layer which comprises the group-III element, the group-V element and nitrogen onto said cap-layer.
15. The process of claim 14 , further comprising, subsequent to said epitaxially growing said additional well-layer, epitaxially growing an additional cap-layer on said additional well-layer.
16. The process of claim 1 , further comprising, subsequent to epitaxially growing said cap-layer, epitaxially growing onto said cap-layer, sequentially, a plurality of additional well-layers, each independently comprising a group-III element, a group-V element and nitrogen, and a plurality of additional cap layers.
17. The process of claim 1 , wherein said group-III element is selected from the group consisting of gallium, indium, thallium and aluminum.
18. The process of claim 1 , wherein said group-V element is selected from the group consisting of arsenic, antimony and phosphorous.
19. The process of claim 1 , wherein said precursor of nitrogen is selected from the group consisting of dimethylhydrazine (DMH), ammonia, hydrazine, monomethylhydrazine, t-butylhydrazine, phenylhydrazine, t-butylamine and nitrogen trifluoride.
20. The process of claim 1 , wherein said group-III element is indium and said precursor of said group-III element is trimethylindium (In(CH 3 ) 3 ).
21. The process of claim 1 , wherein said group-III element is gallium and said precursor of said group-III element is trimethylgalium (Ga(CH 3 ) 3 ).
22. The process of claim 1 , wherein said group-V element is arsenic and said precursor of said group-III element is arsine (ArH 3 ), t-butylarsine (t-BuAsH 2 ), and tri-t-butylarsine.
23. A quantum well structure comprising a base-layer and a well-layer which comprises a group-III element, a group-V element and nitrogen, and a cap layer, the quantum well structure being produced by the process of claim 1 .