Light absorbing layer for II-VI semiconductor light emitting devices

#The present invention relates to II-VI semiconductor devices such as laser diodes and light emitting diodes. More specifically, the present invention relates to a light absorbing layer for a II-VI semiconductor light emitting device.

#Buried ridge (buried heterostructure) semiconductor devices are known. Such devices are useful in constructing light emitting or detecting devices, diodes and laser diodes such as those described in U.S. Pat. No. 5,213,998, issued May 25, 1993; U.S. Pat. No. 5,248,631, issued Sep. 28, 1993; U.S. Pat. No. 5,274,269, issued Dec. 28, 1993; U.S. Pat. No. 5,291,507, issued Mar. 1, 1994; U.S. Pat. No. 5,319,219, issued Jun. 7, 1994; U.S. Pat. No. 5,395,791, issued Mar. 7, 1995; U.S. Pat. No. 5,396,103, issued Mar. 7, 1995; U.S. Pat. No. 5,404,027, issued Apr. 4, 1995; U.S. Pat. No. 5,363,395, issued Nov. 8, 1994; U.S. Pat. No. 5,515,393, issued May 7, 1996; U.S. Pat. No. 5,420,446, issued May 30, 1995; U.S. Pat. No. 5,423,943, issued Jun. 13, 1995; U.S. Pat. No. 5,538,918, issued Jul. 23, 1996; and U.S. Pat. No. 5,513,199, issued Apr. 30, 1996.

#Historically, laser diodes have generated infrared or red light. However, there are many applications where diodes which emit radiation in shorter wavelengths, for example, in the blue and green portions of the spectrum (i.e., at wavelengths between 590 nm and 430 nm) would be useful. Further, such short wavelength laser diodes would increase the performance and capabilities of many existing systems which currently use infrared and red laser diodes.

#FIG. 1 is a simplified cross-sectional view of a light emitting device including a thick light absorbing layer in accordance with one embodiment of the present invention.

#FIG. 2 is a simplified cross-sectional view of a light emitting device in accordance with another embodiment having a thin light absorbing layer spaced apart from a ridge of the device.

#FIG. 3 is a simplified cross-sectional view of a light emitting device in accordance with another embodiment having a layer of high index, low loss material deposited upon the light absorbing layer.

#The present invention provides reduced dark line defects (DLDs) in II-VI semiconductor light emitting devices. In the present invention, an absorbing layer is provided in a II-VI semiconductor device which absorbs extraneous light and thereby reduces generation of dark line defects.

#FIG. 1 is a simplified cross-sectional view of a laser diode 10 which is one example of II-VI semiconductor device in accordance with the present invention. Laser diode 10 includes GaAs substrate 12 which carries an ZnSe buffer layer 14. A MgZnSSe cladding layer 16 is carried on layer 14. A quantum well layer 18, for example CdZnSe, is sandwiched between guide layers 20 and 22, for example ZnSSe, carried on cladding layer 16. A second cladding layer 24 of MgZnSSe is deposited on guiding layer 22 and carries a p-type contact 26 having a layer 28 of ZnSeTe and a layer 30 of Pd-Au. A contact layer 32 of Ti-Au is deposited thereon.

#In accordance with one aspect of the present invention, device 10 of FIG. 1 includes an absorbing layer 34 which is deposited on guiding layer 22 in those areas where cladding layer 24 is not present. In the embodiment of FIG. 1, absorbing layer 34 completely surrounds cladding layer 24.