Semiconductor light emitting device having a semiconductor layer formed by selective growth

#The present invention relates to semiconductor light emitting devices and processes for producing same. More particularly, the present invention relates to a semiconductor light emitting device, a display unit, a method of fabricating a semiconductor light emitting device, and a method of fabricating a semiconductor laser having wurtzite type compound semiconductor layers such as GaN based semiconductor layers that are formed by selective growth.

#Conventionally, when manufacturing a semiconductor light emitting device, a semiconductor laser device or a light emitting diode is fabricated by forming a selection mask on a sapphire substrate and selectively growing a semiconductor layer made from a nitride such as gallium nitride through an opening in the selection mask. Sapphire is often used as a substrate for growing gallium nitride. However, dislocations often occur in the crystals, at a high density, due to mismatches between the crystal lattices of the sapphire substrate and gallium nitride. The following methods are known to reduce crystal defects: a method of forming a low temperature buffer layer on a substrate; a method of combining usual crystal growth with selective crystal growth in the lateral direction (ELO: Epitaxial Lateral Overgrowth as described in Japanese Patent Laid-open No. Hei 10-312971); and a method of forming a gallium nitride based semiconductor laser, in which stacked layers having tilt planes are formed by selective growth (see Japanese Patent Laid-open No. Hei 11-312840).

#Conventionally, an image display unit is configured by arranging pixels in a matrix. Each pixel is composed of a combination of light emitting diodes or semiconductor lasers of blue, green and red. An image is displayed by independently driving the respective pixels. The image display unit can be also used as a white light emitting unit or an illumination unit by allowing the light emitting devices of blue, green, and red to simultaneously emit light of blue, green, and red. In particular, since a light emitting device using a nitride based semiconductor has a band gap energy ranging from about 1.9 eV to about 6.2 eV, a number of light emitting devices capable of emitting light of many colors can be fabricated using only semiconductor layers made from one kind of material (i.e., the nitride based semiconductor), thereby easily realizing a full-color display. Multi-color light emitting devices using nitride based semiconductors have been studied extensively. It is to be noted that the term “nitride” used herein describes a compound which contains one or more of B, Al, Ga, In, and Ta as group III elements and N as a group V element, and which may contain impurities in an amount of about 1% or less of the total amount or about 1×1020 cm3 or less.

#FIG. 1A is a plan view of a semiconductor light emitting device according to a first embodiment of the present invention, showing a state of the device before and after selective growth from an opening of a selection mask which is formed in such a manner as to extend in a (1-100) direction or a (11-20) direction, and FIG. 1B is a sectional view taken on line b—b of FIG. 1A.

#FIG. 2 is a side view of a portion of the semiconductor light emitting device according to the first embodiment, showing one of the tilt planes of the semiconductor layers and an electrode formed thereon.

#FIG. 3A is a plan view of a semiconductor light emitting device according to a second embodiment of the present invention, showing a state of the device before and after selective growth from an opening of a selection mask which is formed in such a manner as to extend with its longitudinal direction tilted from the (1-100) direction or the (11-20) direction by a slight angle, and FIG. 3B is a sectional view taken on line b—b of FIG. 3A.

#A semiconductor light emitting device according to an embodiment of the present invention is manufactured by forming a selection mask having a stripe-shaped opening portion on a base body, forming a semiconductor layer having a ridge line parallel to long-sides of the stripe-shaped opening portion by selective growth from the opening portion of the selection mask, and stacking a first conductive type cladding layer, an active layer, and a second conductive layer on the semiconductor layer.

#The base body used for a semiconductor light emitting device according to an embodiment of the present invention is not particularly limited insofar as a wurtzite type compound semiconductor layer can be formed thereon. For example, a substrate made from sapphire (Al2O3, whose desirable crystal plane is an A-plane, R-plane, or C-plane), SiC (having a structure of 6H, 4H or 3C), GaN, Si, ZnS, ZnO, AlN, LiMgO, LiGaO2, GaAs, MgAl2O4, or InAlGaN can be used as the base body. Preferably, the material used for forming the base body has a hexagonal or cubic system, and more preferably, has the hexagonal system. When using a sapphire substrate, preferably a sapphire substrate with the C-plane of sapphire taken as a principal plane thereof, which has been often used for growing a gallium nitride (GaN) based compound semiconductor thereon, is used. It is to be noted that the C-plane of sapphire taken as the principal plane of the substrate in the present invention may be tilted from the strict C-plane by an angle ranging from about 5° to about 6°. A silicon substrate, which has been widely used for fabricating semiconductor devices, may be also used as the base body.

#It is noted that the plane terminology (e.g., S-plane, C-plane or the like) as used herein denotes crystal planes in accordance with Miller indices of a hexagonal crystal system. Where appropriate, throughout the specification, these planes are intended to include more than one plane in the hexagonal crystal system. For example, the S-plane is listed above as corresponding to the (1-101) plane, but it should be understood that, where appropriate, the S-plane is intended to include one or more of the planes relating to the family of planes making up a crystal structure having the S-plane. For example, if the crystal structure being described is a hexagonal pyramid having the S-plane, planes corresponding to each side face of the hexagonal pyramid would be included in the family of planes denoted by the S-plane. For example, in addition to the (1-101) plane, a hexagonal pyramid has side faces corresponding to the (10-11), (01-11), (-1101) and (0-111) planes.