Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – With heterojunction
Reexamination Certificate
2003-02-24
2004-12-14
Thomas, Tom (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
With heterojunction
C257S102000, C257S079000, C257S080000, C257S082000, C257S085000, C257S096000, C438S022000, C438S046000, C438S047000
Reexamination Certificate
active
06831304
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a boron-phosphide-based semiconductor device having a hetero junction structure; and particularly to a boron-phosphide-based semiconductor light-emitting device exhibiting high emission intensity and method for producing the same.
Boron phosphide (BP) has been traditionally known as a Group III-V compound semiconductor (see Nature, 179, No. 4569 (1957), p. 1075). Since boron phosphide (BP) is an indirect-transition-type semiconductor (see “An Introduction to Semiconductor Device” authored by Iwao Teramoto, first edition, published by Baifukan Co., Ltd. on Mar. 30, 1995, p. 28), BP is considered to be unsuitable for use as a material for formation of a light-emitting layer of a semiconductor light-emitting device. In a conventional boron-phosphide-based semiconductor light-emitting diode (LED) incorporating a boron-phosphide-based semiconductor layer, the boron-phosphide-based semiconductor layer formed of, for example, boron phosphide serves therefore as a buffer layer provided on a single-crystal silicon substrate (see U.S. Pat. No. 6,069,021). Meanwhile, in a laser diode (LD), a boron-phosphide-based semiconductor layer serves as, for example, a contact layer for formation of an ohmic electrode (see Japanese Patent Application Laid-Open (kokai) No. 2-288388).
In general, a light-emitting layer of a semiconductor light-emitting device is formed of a direct-transition-type semiconductor material, which exhibits higher radiative recombination efficiency as compared with an indirect-transition-type semiconductor. In many cases, a light-emitting layer of a boron-phosphide-based semiconductor LED has been conventionally formed of gallium indium nitride (Ga
X
In
1−X
N:0≦X≦1) (see Japanese Patent Publication (kokoku) No. 55-3834). A light-emitting layer has been formed especially from Ga
X
In
1−X
N(0≦X≦1) which is intentionally doped with an element belonging to Group IV of the periodic table, such as silicon (Si) or germanium (Ge) (see Japanese Patent Application Laid-Open (kokai) No. 6-260680). This is because doping with a Group IV element has been disclosed as producing a Ga
X
In
1−X
N(0≦X≦1) light-emitting layer of high emission intensity (see Japanese Patent No. 2560963). In order to produce a semiconductor light-emitting device exhibiting high emission intensity, a light-emitting portion thereof is generally formed of a pn-junction-type double hetero (DH) structure including a light-emitting layer, and p-type and n-type cladding layers which sandwich the light-emitting layer (see Japanese Patent Application Laid-Open (kokai) No. 6-260283).
Conventionally, a p-type boron-phosphide-based semiconductor layer has generally been formed through intentional doping with an element belonging to Group II of the periodic table, such as magnesium (Mg) or zinc (Zn) (see (1) Japanese Patent Application Laid-Open (kokai) No. 2-275682, (2) Japanese Patent Application Laid-Open (kokai) No. 2-288371, (3) Japanese Patent Application Laid-Open (kokai) No. 2-288388, (4) Japanese Patent Application Laid-Open (kokai) No. 10-242514, (5) Japanese Patent Application Laid-Open (kokai) No. 10-242515, and (6) Japanese Patent Application Laid-Open (kokai) No. 10-242567). Meanwhile, an n-type boron-phosphide-based semiconductor layer has generally been formed through doping with a Group IV element such as silicon (Si) (see, for example, Japanese Patent Application Laid-Open (kokai) No. 2-288388). In view of the foregoing, a p-type cladding layer constituting a light-emitting portion of pn-junction-type DH structure has been formed of a p-type boron-phosphide-based semiconductor layer doped with, for example, Mg or Zn. Meanwhile, an n-type cladding layer has been formed of an n-type boron-phosphide-based semiconductor layer doped with silicon (see Japanese Patent Application No. 2001-158282).
Silicon (Si), which is a Group IV element, is described as serving as an amphoteric impurity in a boron-phosphide-based semiconductor, as well as in other Group III-V compound semiconductors (see “
Handotai Gijutsu
(
Jo
)” authored by Katsufusa Shohno, ninth printing, published by University of Tokyo Press on Jun. 25, 1992, p. 77). Regarding a boron phosphide semiconductor layer, a technique for formation of an n-type or p-type boron phosphide semiconductor layer which is not intentionally doped; i.e., an undoped boron phosphide semiconductor layer, by appropriately determining the vapor-phase growth temperature of the semiconductor layer (see the aforementioned “Handotai Gijutsu (
Jo
),” pp. 76-77) has been proposed. Boron vacancies and phosphorus vacancies are considered to determine the conduction type of an undoped boron phosphide semiconductor layer (see “100 Semiconductor Techniques in the Super LSI Generation [III]” authored by Katsufusa Shohno, appendix of a magazine “Electronics,” Vol. 27, No. 4, published by Ohmsha, Ltd. on Apr. 1, 1982, pp. 86-87).
Boron-phosphide-based semiconductor layers having different conduction types have been conventionally formed through doping with dopants of different types. When a pn-junction structure including a boron-phosphide-based semiconductor layer is produced, an intricate doping process employing different dopants is therefore required for formation of n-type and p-type boron-phosphide-based semiconductor layers. Even when an attempt is made to produce a light-emitting portion of pn-junction-type DH structure incorporating an undoped boron-phosphide-based semiconductor layer serving as a cladding layer to avoid the intricate doping process, diffusion of a Group IV element (i.e., dopant) from a light-emitting layer into the undoped boron-phosphide-based semiconductor cladding layer cannot be completely prevented. The intensity of light emitted from the light-emitting layer becomes inconsistent because of variation in the diffusion amount of the Group IV element, such as silicon, doped to a light emitting layer for enhancement of emission intensity, into an undoped boron-phosphide-based semiconductor layer. The resultant boron-phosphide-based semiconductor light-emitting device fails therefore to exhibit homogeneous emission intensity.
SUMMARY OF THE INVENTION
In the boron-phosphide-based semiconductor light-emitting device having a pn-junction-type DH structure including a light-emitting layer formed of a semiconductor layer doped with an appropriate amount of a Group IV element (i.e., a dopant for enhancing emission intensity), a boron-phosphide-based semiconductor light-emitting device exhibiting homogeneous and high emission intensity is advantageously produced provided that diffusion of the Group IV element into an undoped boron-phosphide-based semiconductor layer which is readily formed can be suppressed, thereby preventing reduction of the amount of the Group IV element contained in the light-emitting layer.
An object of the present invention is to provide a light-emitting portion of hetero junction structure which is employed for producing a boron-phosphide-based semiconductor light-emitting device exhibiting high emission intensity.
Accordingly, the above object of the present invention has been achieved by providing the following.
(1) A pn-junction-type boron-phosphide-based semiconductor light-emitting device comprising a single-crystal silicon (Si) substrate of first conduction type; a first boron-phosphide-based semiconductor layer of first conduction type formed of an undoped boron-phosphide-based semiconductor of first conduction type containing a Group IV element provided on the substrate; a light-emitting layer provided on the first boron-phosphide-based semiconductor layer, the light-emitting layer formed of a Group III-V semiconductor layer of first or second conduction type which is doped with an element belonging to Group IV of the periodic table provided on the first boron-phosphide-based semiconductor layer; and a second boron-phosphide-based semiconductor layer of second conduction type formed of a boron-phosphide-based semiconductor layer of
Lee Eugene
Showa Denko Kabushiki Kaisha
Sughrue & Mion, PLLC
Thomas Tom
LandOfFree
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