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6027 results about "Heterojunction" patented technology

A heterojunction is the interface that occurs between two layers or regions of dissimilar crystalline semiconductors. These semiconducting materials have unequal band gaps as opposed to a homojunction. It is often advantageous to engineer the electronic energy bands in many solid-state device applications, including semiconductor lasers, solar cells and transistors ("heterotransistors") to name a few. The combination of multiple heterojunctions together in a device is called a heterostructure, although the two terms are commonly used interchangeably. The requirement that each material be a semiconductor with unequal band gaps is somewhat loose, especially on small length scales, where electronic properties depend on spatial properties. A more modern definition of heterojunction is the interface between any two solid-state materials, including crystalline and amorphous structures of metallic, insulating, fast ion conductor and semiconducting materials.

Strain balanced nitride heterojunction transistors

A nitride based heterojunction transistor includes a substrate and a first Group III nitride layer, such as an AlGaN based layer, on the substrate. The first Group III-nitride based layer has an associated first strain. A second Group III-nitride based layer, such as a GaN based layer, is on the first Group III-nitride based layer. The second Group III-nitride based layer has a bandgap that is less than a bandgap of the first Group III-nitride based layer and has an associated second strain. The second strain has a magnitude that is greater than a magnitude of the first strain. A third Group III-nitride based layer, such as an AlGaN or AlN layer, is on the GaN layer. The third Group III-nitride based layer has a bandgap that is greater than the bandgap of the second Group III-nitride based layer and has an associated third strain. The third strain is of opposite strain type to the second strain. A source contact, a drain contact and a gate contact may be provided on the third Group III-nitride based layer. Nitride based heterojunction transistors having an AlGaN based bottom confinement layer, a GaN based channel layer on the bottom confinement layer and an AlGaN based barrier layer on the channel layer, the barrier layer having a higher concentration of aluminum than the bottom confinement layer, are also provided. Methods of fabricating such transistor are also provided.

Solar cell

The present invention provides a thin film amorphous silicon-crystalline silicon back heterojunction and back surface field device configuration for a heterojunction solar cell. The configuration is attained by the formation of heterojunctions on the back surface of crystalline silicon at low temperatures. Low temperature fabrication allows for the application of low resolution lithography and/or shadow masking processes to produce the structures. The heterojunctions and interface passivation can be formed through a variety of material compositions and deposition processes, including appropriate surface restructing techniques. The configuration achieves separation of optimization requirements for light absorption and carrier generation at the front surface on which the light is incident, and in the bulk, and charge carrier collection at the back of the device. The shadowing losses are eliminated by positioning the electrical contacts at the back thereby removing them from the path of the incident light. Back contacts need optimization only for maximum charge carrier collection without bothering about shading losses. A range of elements/alloys may be used to effect band-bending. All of the above features result in a very high efficiency solar cell. The open circuit voltage of the back heterojunction device is higher than that of an all-crystalline device. The solar cell configurations are equally amenable to crystalline silicon wafer absorber as well as thin silicon layers formed by using a variety of fabrication processes. The configurations can be used for radiovoltaic and electron-voltaic energy conversion devices.

High mobility heterojunction complementary field effect transistors and methods thereof

InactiveUS7057216B2High hole mobilitySimilar current carrying capabilityTransistorSolid-state devicesHeterojunctionPresent day
In all representative embodiments presented, the Ge concentration in the source and drain 10 and the SiGe epitaxial channel layer 20 is in the 15% to 50% range, preferably between about 20% to 40%. The SiGe thicknesses in the source / drain 10 are staying below the critical thickness for the given Ge concentration. The critical thickness is defined such that above it the SiGe will relax and defects and dislocations will form. The thickness of the SiGe epitaxial layer 20 typically is between about 5nm and 15nm. The thickness of the epitaxial Si layer 30 is typically between about 5nm and 15nm. FIG. 1A shows an embodiment where the body is bulk Si. These type of devices are the most common devices in present day microelectronics. FIGS. 1B and 1C show representative embodiment of the heterojunction source / drain FET device when the Si body 40 is disposed on top of an insulating material 55. This type of technology is commonly referred to as silicon on insulator (SOI) technology. The insulator material 55 usually, and preferably, is SiO2. FIG. 1B shows an SOI embodiment where the body 40 has enough volume to contain mobile charges. Such SOI devices are called partially depleted devices. FIG. 1C shows an SOI embodiment where the volume of the body 40 is insufficient to contain mobile charges. Such SOI devices are called fully depleted devices. For devices shown in FIG. 1B and 1C there is, at least a thin, layer of body underneath the source and drain 10. This body material serves as the seed material onto which the epitaxial SiGe source and drain 10 are grown. In an alternate embodiment, shown in FIG. 1D. for extremely thin fully depleted SOI devices, one could grow the source and drain 10 laterally, from a lateral seeding, in which case the source and drain 10 would penetrate all the way down to the insulating layer 55.
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