H - Electricity – 01 – L
Patent
H - Electricity
01
L
345/32
H01L 33/00 (2006.01) H01L 21/30 (2006.01) H01L 21/306 (2006.01) H01L 21/78 (2006.01) H01S 5/02 (2006.01)
Patent
CA 1140661
ABSTRACT OF THE DISCLOSURE Double heterostructure (Al,Ga)As wafers comprising layers of gallium arsenide and aluminum gallium arsenide on a metallized n-GaAs substrate are separated into individual devices for use as diode lasers. In contrast to prior art techniques of mechanically cleaving the wafer in mutually orthogonal directions, the wafer is first separated into bars of diodes by a process which comprises (a) etching into the n-GaAs substrate with an anisotropic etchant to form V-grooves in the wafer and (b) mechanically cleaving into bars of diodes. The cleaving may be done by prior art techniques using a knife, razor blade or tweezer edge or by attaching the side of the wafer opposite to the V- grooves to a flexible adhesive tape and rolling the assembly, such as over a tool of small radius. For separating thin wafers (about 3 to 5 mils thick), prior to the anisotropic etching, the wafers are processed by forming an array of exposed lines on the n-side by photolithography to define the lasing ends of the diodes and etching through the exposed metallized portion to expose portions of the underlying N-GaAs. The exposed portions of the wafer are then anisotropically etched to a distance of about 1 to 2 mils less than the total thickness of the wafer. For separating thicker wafers (about 6 to 10 mils thick), prior to the anisotropic etching, the wafers are processed by forming channels of substantially parallel sidewalls about 1 to 4 mils deep into the surface of the n-GaAs substrate. The wafer is then anisotropically etched to a depth sufficient to form V-grooves in the bottom of the channels. Advant- ageously, such thicker wafers, which are cleaved only with great difficulty by prior art techniques, are less susceptible to breaking during handling and permit fabrication of shorter diode (cavity) length, which in turn is related to lower threshold current for device operation. The diode bars may then, following passivation, be further cleaved into individual diodes by the prior art techniques of mechanically scribing and cleaving. Processing in accordance with the invention improves length definition and uniformity, increases device yields and reduces striations on lasing facets, as compared with prior art techniques.
337513
Anderson Stephen J.
Collins David W.
Huggins Harold A.
Scholl Frederick R.
Woolhouse Geoffrey R.
Borden Ladner Gervais Llp
Optical Information Systems Inc.
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