Nitride semiconductor single crystal substrate, and methods of fabricating the same and a vertical nitride semiconductor light emitting diode using the same

Abstract

A nitride semiconductor single crystal substrate, a manufacturing method thereof and a method for manufacturing a vertical nitride semiconductor device using the same. According to an aspect of the invention, in the nitride semiconductor single crystal substrate, upper and lower regions are divided along a thickness direction, the nitride single crystal substrate having a thickness of at least 100 μm. Here, the upper region has a doping concentration that is five times or greater than that of the lower region. Preferably, a top surface of the substrate in the upper region has Ga polarity. Also, according to a specific embodiment of the invention, the lower region is intentionally un-doped and the upper region is n-doped. Preferably, each of the upper and lower regions has a doping concentration substantially identical in a thickness direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIGS. 1 a and 1b are cross-sectional views for explaining a method for manufacturing a conventional nitride single crystal substrate;

FIG. 2 a is a side cross-sectional view illustrating a nitride single crystal substrate according to a first aspect of the invention, and FIG. 2b is a graph illustrating doping concentration of a nitride single crystal substrate in a thickness direction;

FIGS. 3 a to 3d are cross-sectional views for explaining a method for manufacturing a single crystal substrate according to a second aspect of the invention; and

FIGS. 4 a to 4d are cross-sectional views for explaining a method for manufacturing a vertical nitride light emitting device according to a third aspect of the invention.

Claims

1. A nitride single crystal substrate comprising: upper and lower regions divided along a thickness direction, the nitride single crystal substrate having a thickness of at least 100 μm,wherein the upper region has a doping concentration that is five times or greater than that of the lower region.

2. The nitride single crystal substrate according to claim 1, wherein a top surface of the substrate in the upper region has Ga polarity.

3. The nitride single crystal substrate according to claim 1, wherein the lower region is intentionally un-doped and the upper region is n-doped.

4. The nitride single crystal substrate according to claim 3, wherein each of the upper and lower regions has a doping concentration substantially identical in a thickness direction.

5. The nitride single crystal substrate according to claim 3, wherein the upper region has a doping concentration of at least 5×1018/cm3, and the lower region has a doping concentration up to 5×1017/cm3.

6. The nitride single crystal substrate according to claim 1, wherein the substrate has a thickness ranging from 200 μm to 600 μm.

7. The nitride single crystal substrate according to claim 6, wherein the lower region has a thickness ranging from 100 μm to 500 μm.

8. The nitride single crystal substrate according to claim 6, wherein the upper region has a thickness ranging from 10 μm to 100 μm.

9. The nitride single crystal substrate according to claim 1, wherein the nitride single crystal substrate comprises a material having a composition expressed by AlxInyGa(1-x-y)N, where 0≦x≦1, 0≦y≦1, and 0≦x+y≦1.

10. A method for manufacturing a nitride single crystal substrate comprising: preparing a base substrate for growing a nitride single crystal;growing a first nitride single crystal layer on the base substrate;growing a second nitride single crystal layer on the first nitride single crystal layer, the second nitride single crystal layer having a doping concentration that is five times or greater than that of the first nitride single crystal layer; andremoving the base substrate to obtain a nitride single crystal substrate having first and second nitride single crystal layers,wherein the nitride single crystal substrate has a thickness of at least 100 μm.

11. The method according to claim 10, wherein the first and second nitride single crystal layers each are grown to have Ga polarity on a top surface thereof.

12. The method according to claim 10, wherein the first nitride single crystal layer is intentionally undoped and the second nitride single crystal layer is n-doped.

13. The method according to claim 12, wherein each of the first and nitride single layers has a doping concentration substantially identical in a thickness direction.

14. The method according to claim 12, wherein the first nitride single crystal layer has a doping concentration of at least 5×1018/cm3 and the second nitride single crystal layer has a doping concentration up to 5×1017/cm3.

15. The method according to claim 10, wherein the substrate has a thickness ranging from 200 μm to 600 μm.

16. The method according to claim 15, wherein the first nitride single crystal layer has a thickness ranging from 100 μm to 500 μm.

17. The method according to claim 15, wherein the second nitride single crystal layer has a thickness ranging from 10 μm to 100 μm.

18. The method according to claim 10, wherein the first and second nitride single crystal layers comprise a material having a composition expressed by AlxInyGa(1-x-y)N, where 0≦x≦1, 0≦y≦1 and 0≦x+y≦1.

19. The method according to claim 10, wherein the first and second nitride single crystal layers are grown by Hydride Vapor Phase Epitaxy.

20. A method for manufacturing a vertical nitride semiconductor light emitting device comprising: preparing a nitride single crystal substrate having a thickness of at least 100 μm, the nitride single crystal substrate including upper and lower regions along a thickness direction, the upper region doped with first conductive impurities at a concentration five times or greater than that of the lower region;sequentially growing an active layer and a second conductive nitride semiconductor layer on the nitride single crystal substrate;removing the lower region from the nitride single crystal substrate so that the upper region of the nitride single crystal substrate provides an underside surface; andforming a first electrode on the underside surface of the nitride single crystal substrate with the lower region removed therefrom and a second electrode on the second conductive nitride semiconductor layer.

21. The method according to claim 20, wherein the step of sequentially growing the active layer and the second conductive nitride semiconductor layer comprises growing the first conductive nitride semiconductor layer before growing the active layer.

22. The method according to claim 20, wherein the active layer and the second conductive nitride semiconductor layer are sequentially grown by Metal Organic Vapor Phase Epitaxy.

23. The method according to claim 20, wherein a top surface of the substrate in the upper region has Ga polarity.

24. The method according to claim 20, wherein the first conductive impurities comprise an n-dopant and the second conductive impurities comprise a p-dopant.

25. The method according to claim 20, wherein the lower region of the nitride single crystal substrate is intentionally un-doped.

26. The method according to claim 20, wherein each of the upper and lower regions has a doping concentration substantially identical in a thickness direction.

27. The method according to claim 25, wherein the upper region has a doping concentration of at least 5×1018/cm3 and the lower region has a doping concentration up to 5×1017/cm3.

28. The method according to claim 20, wherein the substrate has a thickness ranging from 200 μm to 600 μm.

29. The method according to claim 28, wherein the lower region has a thickness ranging from 100 μm to 500 μm.

30. The method according to claim 28, wherein the upper region has a thickness ranging from 10 μm to 100 μm.