Optical device structure using GaN substrates for laser applications
An optical device includes a gallium nitride substrate member having an m-plane nonpolar crystalline surface region characterized by an orientation of about −1 degree towards (000-1) and less than about +/−0.3 degrees towards (11-20). The device also has a laser stripe region formed overlying a portion of the m-plane nonpolar crystalline orientation surface region. In a preferred embodiment, the laser stripe region is characterized by a cavity orientation that is substantially parallel to the c-direction, the laser stripe region having a first end and a second end. The device includes a first cleaved c-face facet, which is coated, provided on the first end of the laser stripe region. The device also has a second cleaved c-face facet, which is exposed, provided on the second end of the laser stripe region.
1. A method for forming an optical device comprising:
providing a gallium and nitrogen containing substrate member having a {20-21} crystalline surface region characterized by an off-cut orientation of −8 degrees to −2 degrees or 2 degrees to 8 degrees toward a c-plane, the gallium and nitrogen containing substrate member having a laser stripe region overlying a portion of the crystalline surface region, the laser stripe region having a first end and a second end;
forming a first cleaved facet on the first end of the laser stripe region, the first cleaved facet having first laser scribed regions extending intermittently along a first upper edge of the first cleaved facet to provide a first saw tooth profile, wherein each of the first laser scribed regions forms a tooth of the first saw tooth profile, each of the first laser scribed regions is spaced from adjacent ones of the first laser scribed regions by smooth surfaces of the first cleaved facet, and a depth that the first laser scribed regions extend downward from the first upper edge toward the {20-21} crystalline surface region varies across the first cleaved facet; and
forming a second cleaved facet on the second end of the laser stripe region, the second cleaved facet having second laser scribed regions extending intermittently along a second upper edge of the second cleaved facet to provide a second saw tooth profile, wherein each of the second laser scribed regions forms a tooth of the second saw tooth profile, each of the second laser scribed regions is spaced from adjacent ones of the second laser scribed regions by smooth surfaces of the second cleaved facet, and a depth that the second laser scribed regions extend downward from the second upper edge toward the {20-21} crystalline surface region varies across the second cleaved facet.
2. The method of claim 1 wherein the first cleaved facet is substantially parallel with the second cleaved facet.
3. The method of claim 1 wherein the first cleaved facet comprises a first mirror surface.
4. The method of claim 3 wherein the first mirror surface is provided by a scribing and breaking process from either a front side or a backside of the gallium and nitrogen containing substrate member.
5. The method of claim 3 wherein the first mirror surface comprises a coating to modify the reflection characteristic.
6. The method of claim 5 wherein the coating is selected from silicon dioxide, hafnia, titania, tantalum pentoxide, and Al 2 O 3 .
7. The method of claim 1 wherein the second cleaved facet comprises a second mirror surface.
8. The method of claim 7 wherein the second mirror surface is provided by a scribing and breaking process.
9. The method of claim 7 wherein the second mirror surface comprises a coating to modify the reflection characteristic.
10. The method of claim 9 wherein the reflective coating is selected from silicon dioxide, hafnia, titania, tantalum pentoxide, and Al 2 O 3 .
11. The method of claim 1 wherein the laser stripe region has a length ranging from about 100 microns to about 2000 microns.
12. The method of claim 1 wherein the laser stripe region has a width ranging from about 1 micron to about 15 microns.
13. The method of claim 1 wherein spontaneously emitted light is polarized perpendicular to the c-direction.
14. The method of claim 1 wherein spontaneously emitted light is characterized by a wavelength ranging from about 385 to about 420 nanometers.
15. The method of claim 1 wherein spontaneously emitted light is characterized by a wavelength ranging from about 420 to about 460 nanometers.
16. The method of claim 1 wherein spontaneously emitted light is characterized by a wavelength ranging from about 460 to about 500 nanometers.
17. The method of claim 1 wherein spontaneously emitted light is characterized by a wavelength ranging from about 500 to about 550 nanometers.