Manufacture of a semiconductor device
A method of fabricating the active region of a semiconductor light-emitting device, in which the active region comprises a plurality of barrier layers ( 11,13,15,17 ) with each pair of barrier layers being separated by a quantum well layer ( 12,14,16 ), comprises annealing each barrier layer ( 11,13,15,17 ) separately. Each barrier layer ( 11,13,15,17 ) is annealed once it has been grown, and before a layer is grown over the barrier layer. A device grown by the method of the invention has a significantly higher optical power output than a device made by a convention fabrication process having a single annealing step.
1. A method of fabricating the active region of a semiconductor light-emitting device in a nitride material system, the method comprising, in order, the steps of:
a) growing a first barrier layer;
b) annealing the first barrier layer at a temperature greater than the growth temperature of step (a);
c) growing a first quantum well layer over the first barrier layer;
d) growing a second barrier layer over the first quantum well layer; and
e) annealing the second barrier layer at a temperature greater than the growth temperature of step (d).
2. A method as claimed in claim 1 and comprising the further steps of:
f) growing a second quantum well layer over the second barrier layer,
g) growing a third barrier layer over the second quantum well layer, and
h) annealing the third barrier layer at a temperature greater than the growth temperature of step (g).
3. A method as claimed in claim 1 wherein each annealing step comprises annealing the respective barrier layer at a temperature at least 50° C. greater than the growth temperature of the layer.
4. A method as claimed in claim 2 wherein each annealing step comprises annealing the respective barrier layer at a temperature at least 50° C. greater than the growth temperature of the layer.
5. A method as claimed in claim 1 wherein each barrier layer is a layer of Al x Ga 1−x N (0≦x≦0.4), In x Ga 1−x N (0≦x≦0.05) or AlGaInN.
6. A method as claimed in claim 1 wherein the growth temperature of each barrier layer is at least 500° C.
7. A method as claimed in claim 1 wherein the growth temperature of each barrier layer is less than 1050° C.
8. A method as claimed in claim 1 wherein the annealing temperature of each barrier layer is at least 700° C.
9. A method as claimed in claim 1 wherein the annealing temperature of each barrier layer is at least 850° C.
10. A method as claimed in claim 1 wherein the annealing temperature of each barrier layer is less than 1100° C.
11. A method as claimed in claim 1 wherein the annealing temperature of each barrier layer is less than 1000° C.
12. A method as claimed in claim 1 wherein the growth temperature of the quantum well layer is at least 500° C.
13. A method as claimed in claim 1 wherein the growth temperature of the quantum well layer is less than 850° C.
14. A method as claimed in claim 1 wherein the quantum well layer comprises a layer of In x Ga 1−x N (0≦x≦0.3), Al x Ga 1−x N (0≦x≦0.1) or AlGaInN.
15. A method as claimed in claim 1 wherein the device is a light-emitting diode.
16. A method as claimed in claim 1 wherein the device is a laser device.