A Gunn diode is disclosed which comprises a first contact layer (110), a second contact layer (120), and an active layer (130) based on a gallium nitride (GaN) semiconductor material having a base surface (132) and a side surface (135) non-parallel thereto. Optionally, related materials such as aluminum indium gallium nitride (AlInGaN) materials may also be used as the active layer. The first contact layer (110) electrically contacts the side surface (135) to form a side contact (115). The second contact layer (120) forms an electrical contact for the base surface (132), so that a maximum of the electric field strength is formed when an electric voltage is applied between the first contact layer (110) and the second contact layer (120) at the side contact (115).

The present invention provides a terahertz oscillator utilizing a GaN Gunn diode. A terahertz wave is generated in the active layer of the Gunn diode fabricated on GaN substrate. A GaN substrate is designed to act as a waveguide of the terahertz wave. Since the waveguide and the Gunn diodes are integrated, the terahertz wave generated in the active layer couples well with the waveguide made of the GaN substrates. The terahertz wave is emitted from the edge of the waveguide efficiently. To ensure high-reliability through reduction of radiation loss and mitigation of electromigration of anode metal, a GaN substrate with low dislocation density is used. The dislocation density of the GaN substrate is less than 1×10.sup.6 cm.sup.−2. Particularly, usage of a GaN substrate made by the ammonothermal method is preferred.

The present invention provides a terahertz oscillator utilizing a GaN Gunn diode. A terahertz wave is generated in the active layer of the Gunn diode fabricated on GaN substrate. A GaN substrate is designed to act as a waveguide of the terahertz wave. Since the waveguide and the Gunn diodes are integrated, the terahertz wave generated in the active layer couples well with the waveguide made of the GaN substrates. The terahertz wave is emitted from the edge of the waveguide efficiently. To ensure high-reliability through reduction of radiation loss and mitigation of electromigration of anode metal, a GaN substrate with low dislocation density is used. The dislocation density of the GaN substrate is less than 1×10.sup.6 cm.sup.−2. Particularly, usage of a GaN substrate made by the ammonothermal method is preferred.

Systems and methods for forming a mm wave resonant filter include a lithographically fabricated high Q resonant structure. The resonant structure may include a plurality of cavities, each cavity having a characteristic frequency that defines its passband. A filter may include a plurality of resonant structures, and each resonant structure may include a plurality of cavities. These cavities and filters may be fabricated lithographically.

The invention relates to a Gunn diode comprising a first contact layer (110); a second contact layer (120); an active layer (130) based on a gallium nitride (GaN)-based semiconductor material, said active layer being formed between the first contact layer (110) and the second contact layer (120); a substrate (140) on which the active layer (130) is formed together with the first contact layer (110) and the second contact layer (120); and an optical inlet (150) for a laser (50) in order to facilitate or trigger a charge carrier transfer between extrema (210, 220) of the energy bands of the active layer (130) by means of laser irradiation.

Systems and methods for forming a mm wave resonant filter include a lithographically fabricated high Q resonant structure. The resonant structure may include a plurality of cavities, each cavity having a characteristic frequency that defines its passband. A filter may include a plurality of resonant structures, and each resonant structure may include a plurality of cavities. These cavities and filters may be fabricated lithographically.

Systems and methods for forming a compact gas sensor include using a lithographically fabricated high Q resonator coupled to at least one of a Gunn diode and an IMPATT diode. The resonator may include a plurality of cavities filled with a sample gas. A detector coupled to the resonator may measure the amplitude of the emitted mm wave radiation.

Provided is a multi-negative differential resistance device. The multi-negative differential resistance device includes a first negative differential resistance device and a second negative differential resistance device connected in parallel with the first negative differential resistance device, and a peak and a valley of the first negative differential resistance device and a peak and a valley of the second negative differential resistance device are synthesized, and, thus, the multi-negative differential resistance device has two peaks and two valleys.

The invention relates to a Gunn diode comprising a first contact layer (110); a second contact layer (120); an active layer (130) based on a gallium nitride (GaN)-based semiconductor material, said active layer being formed between the first contact layer (110) and the second contact layer (120); a substrate (140) on which the active layer (130) is formed together with the first contact layer (110) and the second contact layer (120); and an optical inlet (150) for a laser (50) in order to facilitate or trigger a charge carrier transfer between extrema (210, 220) of the energy bands of the active layer (130) by means of laser irradiation.

A rectifier is provided for converting an oscillating electromagnetic field into a direct current and comprises an electrically conductive antenna layer configured to absorb electromagnetic radiation, an electrically conductive mirror layer configured to provide an electromagnetic mirror charge of the antenna layer, an electrically insulating tunnel barrier layer positioned between the antenna layer and the mirror layer, and an electronic circuit electrically connected between the conductive mirror layer and the conductive antenna layer. The rectifier employs a metamaterial configuration for room temperature rectification of radiation in regions of the electromagnetic spectrum comprising the MWIR and LWIR regions. Methods for use of the rectifier in rectifying and detecting radiation are described.