# US 7,608,901 B2 · Spin transistor using stray magnetic field > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,608,901 B2 - Document ID: US7608901B2 - Status: Granted - Kind: B2 - Application number: 11/777,228 - Filed: 2007-07-12 - Published: 2008-07-17 - Granted: 2009-10-27 - Earliest claimed: 2007-07-12 - Assignees: Korea Institute of Science and Technology - Inventors: Hyun Cheol Koo; Jong Hwa Eom; Suk Hee Han; Joon Yeon Chang; Hyung Jun Kim - Web page: https://patentgrep.com/patent/US7608901B2 ## CPC - H10D 48/385: {Devices using spin-polarised carriers} - G11C 11/16: using elements in which the storage effect is based on magnetic spin effect - H10D 62/149: {Source or drain regions of field-effect devices} - Y10S 257/902: FET with metal source region - Y10S 977/933: Spintronics or quantum computing - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES - G11C: STATIC STORES (semiconductor memory devices H10B) - Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS ## Abstract Disclosed herein is a spin transistor including: a semiconductor substrate having a channel layer formed therein; first and second electrodes which are formed to be spaced apart from each other on the substrate at a predetermined distance along a longitudinal direction of the channel layer; a source and drain which include magnetized ferromagnetic materials and are formed to be spaced apart form each other between the first electrode and the second electrode at a predetermined distance along the longitudinal direction of the channel layer; and a gate which is formed on the substrate between the source and the drain, and adjusts spin orientations of electrons passing through the channel layer, wherein the electrons passing through the channel layer are spin-aligned at a lower side of the source by a stray magnetic field of the source and spin-filtered at a lower side of the drain by a stray field of the drain. ## Claims ### Claim 1 A spin transistor comprising: a semiconductor substrate having a channel layer formed therein; first and second electrodes which are formed to be spaced apart from each other on the substrate at a predetermined distance along a longitudinal direction of the channel layer; a first ferromagnetic region and a second ferromagnetic region which include magnetized ferromagnetic materials and are formed to be spaced apart form each other between the first electrode and the second electrode at a predetermined distance along the longitudinal direction of the channel layer, the first and second ferromagnetic regions being physically separated from the first and second electrodes and producing stray magnetic fields vertical to a top surface of the channel layer; and a gate which is formed on the substrate between the first and second ferromagnetic regions, and adjusts spin orientations of electrons passing through the channel layer, wherein the gate is insulated from the substrate by a gate oxide on the substrate, and the first and second ferromagnetic regions are disposed below the level of the gate oxide, wherein the electrons passing through the channel layer are spin-aligned at a lower side of the first ferromagnetic region by a stray magnetic field of the first ferromagnetic region and spin-filtered at a lower side of the second ferromagnetic region by a stray magnetic field of the second ferromagnetic region. ### Claim 2 (depends on 1) The spin transistor according to claim 1, further comprising a high-permeability material which is formed to be spaced apart from the first and second ferromagnetic regions at a respective predetermined gap such that a space for spin-alignment and spin-filtering is provided between the first and second ferromagnetic regions, wherein the high-permeability material is formed between the gate and the channel layer. ### Claim 3 (depends on 2) The spin transistor according to claim 2, wherein the high-permeability material is a mu-metal. ### Claim 4 (depends on 1) The spin transistor according to claim 1, wherein the substrate has a ridge structure in which parts of the both sides of the channel layer are cut out in the longitudinal direction of the channel layer and the width of the channel layer is defined by the ridge structure. ### Claim 5 (depends on 4) The spin transistor according to claim 4, wherein an insulating layer for planarization is formed on the cut-out parts of the ridge structure. ### Claim 6 (depends on 5) The spin transistor according to claim 5, wherein the insulating layer includes SiO2 or TaO2. ### Claim 7 (depends on 1) The spin transistor according to claim 1, wherein the channel layer of the substrate includes a two-dimensional electron gas layer. ### Claim 8 (depends on 7) The spin transistor according to claim 7, wherein the two-dimensional electron gas layer includes a material selected from a group of GaAs, InAs and InGaAs. ### Claim 9 (depends on 1) The spin transistor according to claim 1, wherein the substrate further comprises upper and lower cladding layers which are respectively formed above and below the channel layer. ### Claim 10 (depends on 9) The spin transistor according to claim 9, wherein each of the upper and lower cladding layers includes a double cladding layer which has a two-layer structure including an InGaAs layer and an InAlAs layer. ### Claim 11 (depends on 9) The spin transistor according to claim 9, wherein the substrate further comprises an InAlAs carrier supplying layer formed below the lower cladding layer. ### Claim 12 (depends on 9) The spin transistor according to claim 9, wherein the substrate further comprises an InAs capping layer formed on the upper cladding layer. ### Claim 13 (depends on 1) The spin transistor according to claim 1, wherein at least one of the first and second ferromagnetic regions includes ferromagnetic metal. ### Claim 14 (depends on 13) The spin transistor according to claim 13, wherein the ferromagnetic metal is selected from a group of Fe, Co, Ni, CoFe, NiFe and a combination thereof. ### Claim 15 (depends on 1) The spin transistor according to claim 1, wherein at least one of the first and second ferromagnetic regions includes a ferromagnetic semiconductor or a diluted magnetic semiconductor. ### Claim 16 (depends on 15) The spin transistor according to claim 15, wherein the ferromagnetic semiconductor is (Ga, Mn)As. ### Claim 17 (depends on 1) The spin transistor according to claim 1, wherein magnetization directions of the first and second ferromagnetic regions are parallel to the longitudinal direction of the channel layer, and are opposite to each other. ### Claim 18 (depends on 1) The spin transistor according to claim 1, wherein magnetization directions of the first and second ferromagnetic regions are vertical to the top surface of the channel layer. ### Claim 19 (depends on 18) The spin transistor according to claim 18, wherein the magnetization directions of the first and second ferromagnetic regions are equal to each other. ### Claim 20 A spin transistor comprising: a semiconductor substrate having a channel layer formed therein; first and second electrodes which are formed to be spaced apart from each other on the substrate at a predetermined distance along a longitudinal direction of the channel layer; a first ferromagnetic region and a second ferromagnetic region which include magnetized ferromagnetic materials and are formed to be spaced apart form each other between the first electrode and the second electrode at a predetermined distance along the longitudinal direction of the channel layer, the first and second ferromagnetic regions being physically separated from the first and second electrodes and producing stray magnetic fields vertical to a top surface of the channel layer; and a gate which is formed on the substrate between the first and second ferromagnetic regions, and adjusts spin orientations of electrons passing through the channel layer, wherein the gate is insulated from the substrate by a gate oxide on the substrate, and the first and second ferromagnetic regions are disposed below the level of the gate oxide, wherein the electrons passing through the channel layer are spin-aligned at a lower side of the first ferromagnetic region by a stray magnetic field of the first ferromagnetic region and spin-filtered at a lower side of the second ferromagnetic region by a stray magnetic field of the second ferromagnetic region, and the electrons which arrive at the lower side of the second ferromagnetic region are spin-adjusted to be parallel or anti-parallel to the direction of the stray magnetic field of the second ferromagnetic region by a voltage applied to the gate, in order to control an ON/OFF operation of the spin transistor. ### Claim 21 A spin transistor comprising: a semiconductor substrate having a channel layer formed therein; first and second electrodes which are formed to be spaced apart from each other on the substrate at a predetermined distance along a longitudinal direction of the channel layer; a first ferromagnetic region and a second ferromagnetic region which include magnetized ferromagnetic materials and are formed to be spaced apart form each other between the first electrode and the second electrode at a predetermined distance along the longitudinal direction of the channel layer, the first and second ferromagnetic regions being physically separated from the first and second electrodes and producing stray magnetic fields vertical to a top surface of the channel layer; and a gate which is formed on the substrate between the first and second ferromagnetic regions, and adjusts spin orientations of electrons passing through the channel layer, wherein the gate is insulated from the substrate by a gate oxide on the substrate, and the first and second ferromagnetic regions are disposed below the level of the gate oxide, wherein the electrons passing through the channel layer are spin-aligned at a lower side of the first ferromagnetic region by a stray magnetic field of the first ferromagnetic region and spin-filtered at a lower side of the second ferromagnetic region by a stray magnetic field of the second ferromagnetic region, the electrons which arrive at the lower side of the second ferromagnetic region are spin-adjusted to parallel or anti-parallel to the direction of the stray magnetic field of the second ferromagnetic region by a voltage applied to the gate, in order to control an ON/OFF operation of the spin transistor, the transistor is turned on when the spin orientation of the electrons which arrive at the lower side of the second ferromagnetic region is anti-parallel to the direction of the stray magnetic field of the second ferromagnetic region.