Active solid-state devices (e.g. – transistors – solid-state diode – Specified wide band gap semiconductor material other than... – Diamond or silicon carbide
Reexamination Certificate
2004-03-08
2004-11-09
Cao, Phat X. (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Specified wide band gap semiconductor material other than...
Diamond or silicon carbide
C257S086000
Reexamination Certificate
active
06815721
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a diamond semiconductor expected to be developed as a light-emitting device and to a diamond semiconductor light-emitting device that uses the semiconductor.
2. Description of the Prior Art
In view of its superior semiconductor and optical characteristics as well as its mechanical, chemical and thermal characteristics, diamond is receiving much attention as a potential material for electronic devices and also for light-emitting devices. In addition to its superior performance and high functionality, diamond can be used under severe conditions under which conventional materials could not be used, and it is receiving much attention for this reason as well.
Particularly in its use as a material for light-emitting devices, diamond is known to have a wide band gap of 5.5 eV and to demonstrate many light-emission centers in this band gap due to various impurity atoms. Therefore, diamond can be applied to light-emitting devices or laser devices that use these light-emission centers in the range from visible light to ultraviolet light. Laser oscillation that utilizes these light-emission centers has actually been confirmed.
Diamond is an indirect transition semiconductor, but it has a characteristic that allows the observation of the light-emission process at room temperature due to a material-specific electronic state referred to as an exciton and not the extrinsic light-emission center of an impurity atom, etc. This light emission due to an exciton is a 235-nm ultraviolet light at room temperature.
Assuming that diamond has the nonlinear optical characteristic in this light-emission process due to excitons that is required for a laser oscillation condition, diamond light-emitting or laser devices that utilize this should be feasible, but though there have been reports of ultraviolet light emission due to excitons in diamond, there have been no findings of nonlinearity to date.
Researches and developments for laser devices have been attempted using various single solid materials in the ultraviolet band in order to realize ultrahigh capacity light memory, but none have been realized to date. Though a number of ultraviolet light-emitting devices that utilize diamond have been proposed, why none has been realized is because of the lack of a viable crystal growth technology for diamond which has the nonlinear characteristic that is key to realizing a light-emitting device.
This invention is proposed as an attempt to the above, and one object thereof is to provide a diamond semiconductor and a diamond semiconductor light-emitting device capable of actually realizing a light-emitting device or laser device by effectively utilizing diamond as an ultraviolet light-emitting material.
SUMMARY OF THE INVENTION
To achieve the above object, the diamond semiconductor of this invention has an exciton light intensity characteristic that varies nonlinearly.
The aforementioned diamond semiconductor includes a diamond thin film of high quality sufficient to emit ultraviolet light at room temperature with energy injection.
The diamond semiconductor light-emitting device of this invention comprises an n-type diamond semiconductor layer, a p-type diamond semiconductor layer, and a high-quality undoped diamond semiconductor layer between the n-type diamond semiconductor layer and the p-type diamond semiconductor layer, wherein an exciton light emission that varies nonlinearly is output from the undoped diamond semiconductor layer when current is injected into electrodes in direct contact with or formed indirectly on the n-type and p-type diamond semiconductor layers.
Further, the diamond semiconductor light-emitting device of this invention comprises a high-quality n-type diamond semiconductor layer, a high-quality p-type diamond semiconductor layer formed on and in contact with the n-type diamond semiconductor layer, and an activation region layer formed in the interface between the n-type and p-type diamond semiconductor layers, wherein an exciton light emission that varies nonlinearly is output from the activation region layer when current is injected into electrodes in direct contact with or formed indirectly on the n-type and p-type diamond semiconductor layers.
As described above, the diamond semiconductor of this invention demonstrates an exciton light-emission intensity characteristic that varies nonlinearly, and therefore it is able to emit ultraviolet light extremely efficiently. Further, since this invention uses a diamond semiconductor with high quality sufficient to emit ultraviolet light at room temperature with energy injection, the threshold of the nonlinear optical characteristic can be made low depending on the level of high quality. Thus, it is possible to emit ultraviolet light with even greater efficiency.
The diamond semiconductor light-emitting device of this invention uses a high-quality undoped diamond semiconductor layer between the n-type and p-type diamond semiconductor layers, and therefore the intensity of the ultraviolet light increases nonlinearly and exponentially as the current is increased, thus facilitating the configuration of an extremely efficient light-emitting device.
Furthermore, since both the n-type and p-type diamond semiconductor layers of the diamond semiconductor light-emitting device of this invention are of high quality and also since the n-type and p-type diamond semiconductor layers are brought in contact, an activation region is formed between the two. Therefore, the intensity of the ultraviolet light also increases nonlinearly and exponentially as the current is increased, thus facilitating the configuration of an extremely efficient light-emitting device.
The above and other objects and other features of this invention are explained clearly below based on the attached drawings.
REFERENCES:
patent: 5420879 (1995-05-01), Kawarada et al.
patent: 5600156 (1997-02-01), Nishibayashi et al.
patent: 07-307487 (1995-11-01), None
Kajimura Koji
Okushi Hideyo
Takeuchi Daisuke
Watanabe Hideyuki
Agency of Industrial Science & Technology, Ministry of Internati
Cao Phat X.
Doan Theresa T.
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