Oxygen-doped Al-containing current blocking layers in active semiconductor devices
View Patent ↗An active semiconductor device, such as, buried heterostructure semiconductor lasers, LEDs, modulators, photodiodes, heterojunction bipolar transistors, field effect transistors or other active devices, comprise a plurality of semiconductor layers formed on a substrate with one of the layers being an active region. A current channel is formed through this active region defined by current blocking layers formed on adjacent sides of a designated active region channel where the blocking layers substantially confine the current through the channel. The blocking layers are characterized by being an aluminum-containing Group III–V compound, i.e., an Al-III–V layer, intentionally doped with oxygen from an oxide source. Also, wet oxide process or a deposited oxide source may be used to laterally form a native oxide of the Al-III–V layer. An example of a material system for this invention useful at optical telecommunication wavelengths is InGaAsP/InP where the Al-III–V layer comprises InAlAs:O or InAlAs:O:Fe. Other materials for the blocking layers may be InAlGaAs or alternating layers or alternating monolayers of AlAs/InAs. Thus, the O-doped blocking layers may be undoped, impurity doped or co-doped with Fe.
1. A method of forming a current blocking layer in an active semiconductor device without incurring any out-diffusion or in-diffusion of dopants from or into the formed blocking layer comprising the steps of:
forming via a first epitaxial growth the device comprising a plurality of semiconductor layers including an intermediate active region;
etching spatially adjacent regions in portions of the semiconductor layers including the active region to form a current channel mesa;
initiating a second epitaxial growth in the etched regions adjacent the mesa comprising:
forming first setback layer comprising a non-aluminum-containing III–V comnound;
forming on the first setback layers a semi-insulating layer of a aluminum-containing III–V compound doped with oxygen; and
forming on the oxygen doped Al-III–V compound layers a second setback layer containing a non-aluminum-containing III–V compound.
2. The method of claim 1 wherein the aluminum-containing III–V compound layer is selected from the group consisting of InAlAs:O, InAlGaAs:O or AlGaAsSb:O, or monolayers of AlAs:O or AlGaAs:O or InAlGaAs:O alternated with InAs.
3. The method of claim 1 wherein the aluminum-containing III–V compound layer is selected from the group consisting of InAlAs:O:Fe, InAlGaAs:O:Fe, or alternating monolayers of AlAs:O:Fe/InP.
4. The method of claim 1 wherein the setback layers are selected from the group consisting of InP, InGaAs and InGaAsP.
5. The method of claim 1 comprising the further step of co-doping the semi-insulating layer with an additional dopant selected from the group consisting of Fe, Ti, Co and Ni.
6. The method of claim 1 comprising the further step of co-doping the semi-insulating layer with an additional dopant selected from the group consisting of Zn, Mg, Si and S.
7. The method of claim 1 including the step of providing a source of oxygen as a dopant comprising an O 2 flow or an oxide having a low vapor pressure.
8. The method of claim 4 wherein the oxide source is NO x or DEALO.
9. The method of claim 1 wherein the step of forming via a semi-insulating layer of a aluminum-containing III–V compound layer comprises the step of forming a plurality of semi-insulating aluminum-containing III–V compound layers wherein the aluminum-containing III–V compound layers are selected from the group of alternating layer sets of InAlAs:O/InAlAs:O:Fe or InAlGaAs:O/InAlAs:O:Fe.
10. The method of claim 1 wherein the step of forming via a semi-insulating layer of a aluminum-containing III–V compound layer comprises the step of forming a plurality of semi-insulating aluminum-containing III–V compound layers wherein at least one of the aluminum-containing III–V compound layers has a higher aluminum content than at least one of the other aluminum-containing III–V compound layers.
11. The method of claim 1 wherein the step of forming via a semi-insulating layer of a aluminum-containing III–V compound layer comprises the step of forming a plurality of semi-insulating aluminum-containing III–V compound layers wherein at least one of the aluminum-containing III–V compound layers has a different aluminum-containing III–V compound than at least one of said other aluminum-containing III–V compound layers.
12. The method of claim 11 wherein the semi-insulating aluminum-containing III–V compound layers are co-doped with iron.
13. The method of claim 11 wherein the semi-insulating aluminum-containing III–V compound layers are selected from the group consisting of modulated monolayers of AlAs:O, AlGaAs:O, InAlGaAs:O with InAs or InGaAs or AlInGaAs, or alternating layers of InAlAs:O with layers of InAlGaAs:O.
14. The method of claim 13 wherein the semi-insulating aluminum-containing III–compound layers are co-doped with iron.
15. The method of claim 1 wherein the step of forming via a semi-insulating layer of a aluminum-containing III–V compound layer comprises the step of forming a plurality of semi-insulating aluminum-containing III–V compound layers wherein at least one of the aluminum-containing III–V compound layers has a higher aluminum content and is a different aluminum-containing III–V compound than at least one of said other aluminum-containing III–V compound layers.
16. The method of claim 1 wherein the step of forming via a semi-insulating layer of a aluminum-containing III–V compound layer comprises the step of forming a plurality of semi-insulating aluminum-containing III–V compound layers doped with iron or iron and oxygen; and forming on adjacent outer planar sides of the iron doped or iron and oxygen doped Al-III–V compound layers, prior to forming the setback layers, at least one aluminum-containing III–V compound boundary layer doped only with oxygen.
17. The method of claim 16 wherein the aluminum-containing compound layers doped with iron or iron and oxygen are selected from the group of alternating layer sets of InP:Fe, InP:Fe:O, InAlAs:Fe, InAlAs:Fe:O and InAlGaAs:Fe:O.
18. The method of claim 16 wherein the boundary layers are selected from the group consisting of InAlAs:O and InAlGaAs:O.
19. A method of forming a current blocking layer in an active semiconductor device without incurring any out-diffusion or in-diffusion of dopants from or into the formed blocking layer comprising the steps of:
forming via a first epitaxial growth the device comprising a plurality of semiconductor layers including an intermediate active region;
etching spatially adjacent regions in portions of the semiconductor layers including the active region to form a current channel mesa;
initiating a second epitaxial growth in the etched regions adjacent the mesa comprising:
forming a semi-insulating layer of a aluminum-containing III–V compound doped with iron or iron and oxygen; and
forming on the iron doped or iron and oxygen doped Al-III–V compound layers a boundary layer comprising at least one aluminum-containing III–V compound layer doped only with oxygen.
20. The method of claim 19 wherein the at least one aluminum-containing III–V compound layers are selected from the group consisting of InAlAs:O, InAlGaAs:O or AlGaAsSb:O, or monolayers of AlAs:O or AlGaAs:O or InAlGaAs:O alternated with InAs.
21. The method of claim 19 wherein the aluminum-containing III–V compound layers doped with iron or iron and oxygen are selected from the group consisting of InP:Fe, InGaAsP:Fe, InAlAs:Fe, InP:O:Fe, InAlAs:O:Fe, InAlGaAs:O:Fe, or alternating monolayers of AlAs:O:Fe/InP.
22. The method of claim 19 wherein the aluminum-containing III–V compound layers doped with iron or iron and oxygen are selected from the group of alternating layer sets of InAlAs:O:Fe/InAlAs:O:Fe or InAlGaAs:O:Fe/InAlAs:O:Fe.