1. A method ensuring rapid collection of photonically generated charges created in an upper region of a CMOS sensor, while impeding collection of photonically generated charges created in a lower region of said CMOS sensor, the method comprising the following steps:
(a) from time of their generation to time of their collection, moving said charges created in said upper region upward toward a collection region of said sensor, said moving resulting from at least one of (i) drift field resulting from an electric field of at least 1 kVm to urge said charges upward toward a collection region of said sensor, and (ii) diffusion over a diffusion length of less than about 1 \u03bcm; and
(b) from time of their generation, delaying upward movement of substantially all said charges created in said lower region for a time period exceeding recombination lifetime of said charges.
2. The method of claim 1, wherein at step (a)(i), said drift field results from at least one of (1) coupling voltage to a surface region of said CMOS sensor, and (2) creating a doping gradient in said upper region.
3. The method of claim 1, wherein at step (a)(ii) said diffusion results from at least one of (1) thermal energy, and (2) mutual repulsion among said charges.
4. The method of claim 1, wherein step (b) includes subjecting said charges created in said lower region to at least one of (i) a high doping region formed within said sensor, said high doping region having dopant concentration sufficiently high to shorten charge carrier lifetime to a value less than time required for said charges to reach said upper surface, and (ii) a voltage barrier created to inhibit upward movement of said charges toward said upper surface.
5. The method of claim 4, wherein at step (b)(ii) said sensor includes a substrate and an epitaxial layer, and said voltage barrier results from forming said epitaxial layer with a higher dopant concentration than a dopant concentration of said substrate.
6. The method of claim 2, wherein said sensor includes at least one layer of epitaxial material, and said doping gradient results at least in part from difference in doping concentration between said epitaxial material and a layer in said sensor underlying said epitaxial material.
7. The method of claim 2, wherein said sensor includes at least a first layer of epitaxial material and a second layer of epitaxial material, and said doping gradient results at least in part from difference in doping concentration between said first epitaxial material and said second epitaxial material.
8. The method of claim 1, wherein said sensor is a time-of-flight (TOF) sensor.
9. The method of claim 8, wherein at step (a)(i), said drift field results from at least one of (1) coupling voltage to a surface region of said CMOS TOF sensor, and (2) creating a doping gradient in said upper region.
10. The method of claim 8, wherein at step (a)(ii) said diffusion results from at least one of (1) thermal energy, and (2) mutual repulsion among said charges.
11. The method of claim 8, wherein step (b) includes subjecting said charges created in said lower region to at least one of (i) a high doping region formed within said TOF sensor, said high doping region having dopant concentration sufficiently high to shorten charge carrier lifetime to a value less than time required for said charges to reach said upper surface, and (ii) a voltage barrier created to inhibit upward movement of said charges toward said upper surface.
12. The method of claim 11, wherein at step (b)(ii) said TOF sensor includes a substrate and an epitaxial layer, and said voltage barrier results from forming said epitaxial layer with a higher dopant concentration than a dopant concentration of said substrate.
13. The method of claim 9, wherein said TOF sensor includes at least one layer of epitaxial material, and said doping gradient results at least in part from difference in doping concentration between said epitaxial material and a layer of said TOF sensor underlying said epitaxial material.
14. The method of claim 9, wherein said TOF sensor includes at least a first layer of epitaxial material and a second layer of epitaxial material; and said doping gradient results at least in part from difference in doping concentration between said first epitaxial material and said second epitaxial material.
15. A CMOS detector that generates photocharge in response to detection of incoming photonic energy, the detector including:
a substrate having a substrate dopant concentration NS and including an upper substrate surface, and a substrate thickness that includes at least an upper substrate region and a lower substrate region,
a layer of epitaxial material overlying at least a region of said upper substrate surface, and having a epitaxial dopant concentration NE; and
at least one gate structure fabricated on said upper substrate surface, coupleable to a source of bias voltage, and disposed so as to create a first electric field in at least a portion of said upper substrate region;
wherein magnitude of said NS and magnitude of said NE are selected to create a second electric field within said substrate that in combination with said first electric field rapidly conveys photocharges created within said upper substrate region to said upper substrate surface for collection, while substantial numbers of photocharges generated at a depth lower than said upper region recombine without being collected; and
wherein photocharges generated at a depth not exceeding depth of said upper substrate region are photocharges created more recently than photocharges generated within said lower substrate region.
16. The sensor of claim 15, wherein NE>NS.
17. The sensor of claim 15, wherein said first electric field extends downward into at least a portion of said upper substrate region to further hasten collection of more recently generated said photocharge.
18. The sensor of claim 17, wherein photocharges generated in said upper substrate region move upward within said sensor to be collected as a result of at least one characteristic of said sensor selected from (i) coupling a bias voltage to said gate structure creates an electric field exceeding about 1 kVm, which field creates a drift field that moves photocharges created in said upper substrate region upward for collection, and (ii) presence of diffusion over a diffusion length less than about 1 \u03bcm.
19. The sensor of claim 15, further including at least one additional layer of semiconductor material having a layer thickness and having a layer dopant concentration NL, where NE>NL>NS;
wherein magnitude of NL relative to magnitude of NS results in a low drift field within said layer thickness such that charges generated within said lower substrate region that reach said additional layer recombine and perish and will not be collected.
20. The sensor of claim 15, wherein said sensor is a sensor in a time-of-flight (TOF) system, and sensed said photocharges provide a measure of depth distance to a target object imaged by said TOF system.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A magnetic driving apparatus, comprising:
a bi-pole rotor wheel coupled to a speed adjustment motor and comprising a ferromagnetic wheel base and a magnetic rotor, the magnetic rotor including a first magnetic rotor part and a second magnetic rotor part, the first and second magnetic rotor parts being fixed to a circumferential surface of the wheel base in parallel with each other, being spaced a first gap apart from each other, and having opposite magnetic polarities to each other, each of the first and second magnetic rotor parts being formed by arranging alternatively magnetic rectangular blocks and non-magnetic spacers, and when being mounted to a circumferential surface of the ferromagnetic wheel base, the magnetic blocks and non-magnetic spacers of the first magnetic rotor part being aligned with those of the second magnetic rotor part; and
a linear stator which is disposed at a side of the bi-pole rotor wheel, is formed by arranging alternatively magnetic rectangular blocks and non-magnetic spacers on a stator base, and has a width substantially equal to that of the bi-pole rotor wheel,
wherein a space between two adjacent magnetic rectangular blocks of the linear stator is substantially equal to that between two adjacent magnetic rectangular blocks of bi-pole rotor wheel in a circumferential direction of the wheel base,
wherein a second gap is provided between the linear stator and the bi-pole rotor wheel and smaller than the first gap between the first and second magnetic rotor parts, and
wherein the magnetic rotor and the linear stator form a magnetic circuit, and when the speed adjustment motor rotates, a pulling force is generated between the magnetic rotor and the linear stator so as to drive a train.
2. The magnetic driving apparatus according to claim 1, wherein two bi-pole rotor wheels and two linear stators corresponding to the two bi-pole rotor wheels are provided, and the two linear stators are disposed at outsides of the two bi-pole rotor wheels, respectively.
3. The magnetic driving apparatus according to claim 2, further comprising two pairs of guide wheels, wherein the two bi-pole rotor wheels are disposed between and leveled to the two pairs of guide wheels.
4. The magnetic driving apparatus according to claim 1, wherein the second gap between the bi-pole rotor wheel and the linear stator is in a range of approximate 4 mm to 60 mm.
5. The magnetic driving apparatus according to claim 2, wherein the second gap between the bi-pole rotor wheel and the linear stator is in a range of approximate 4 mm to 60 mm.
6. The magnetic driving apparatus according to claim 3, wherein the second gap between the bi-pole rotor wheel and the linear stator is in a range of approximate 4 mm to 60 mm.