Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Magnetic field
Reexamination Certificate
2001-10-26
2003-09-23
Nguyen, Cuong Quang (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Magnetic field
C257S422000, C257S104000
Reexamination Certificate
active
06624490
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a diode and a transistor. More particularly, the present invention relates to a unipolar spin diode and transistor through a mechanism based on inhomogeneous spin polarization.
2. Description of the Related Art
Most semiconductor devices are based on the p-n diode or the transistor. A large class of transistors are the so-called bipolar transistors consisting of back to back p-n diodes either in a p-n-p or n-p-n arrangement. By controlling the chemical potential of the middle region (called the base) the collector current (I
C
) can be varied, and I
C
depends on the base voltage (V
EB
) exponentially.
The development of transistors and its later evolution into the integrated circuit or microchip revolutionized people's daily life and the world. Continuous efforts have been made to find new types of diodes and transistors.
Until recently the emerging field of magneto electronics has focused on magnetic metals for conducting components [1] (hereinafter “[n]” referring to the nth reference in the attached list of references at the end of the specification). Multilayer magnetoelectronic devices, such as giant magnetoresistive (“GMB”) [2,3] and magnetic tunnel junction (MTJ) [4-6] devices, have revolutionized magnetic sensor technology and hold promise for reprogrammable logic and nonvolatile memory applications. The performance of these devices improves as the spin polarization of the constituent material approaches 100%, and thus there are continuing efforts to find 100% spin-polarized conducting materials.
Doped magnetic semiconductors are a promising direction towards such materials, for the bandwidth of the occupied carrier states is narrow. For example, for nondegenerate carriers and a spin splitting of 100 meV the spin polarization will be 98% at room temperature. To date high-temperature (T
Curie
>100K) ferromagnetic semiconductors such as Ga
1-x
.Mn
x
, As are effectively p-doped. Semi-magnetic n-doped semiconductors like BeMnZnSe, however, have already been shown to be almost, 100% polarized (in the case of BeMnZnSe in a 2T external field at 30K) [7]. Both resonant tunneling diodes (RTDs) [8] and light-emitting diodes (LEDs) [9] have been demonstrated which incorporate one layer of ferromagnetic semiconductor. It is inevitable that devices incorporating multiple layers of ferromagnetic semiconducting material will be constructed. Note that “ferromagnetic semiconducting material” or “ferromagnetic semiconductor” as used in this specification includes any magnetic and semi-magnetic semiconductors that is a semiconductor and has a spin polarization, which can be affected by or interact with a magnetic field.
Motivated by this possibility the inventors have investigated the transport properties of specific device geometries based on multilayers of spin-polarized unipolar doped semiconductors. Previous theoretical work in this area includes spin transport in homogeneous semiconductors [10,11] and calculations of spin filtering effects in superlattices [12]. The inventors continued their effort to study the nonlinear transport properties, particularly the behavior of the charge current, of two and three-layer heterostructures, and in particular, developed a unipolar spin diode and transistor through a mechanism based on inhomogeneous spin polarization.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides a unipolar spin diode. In one embodiment of the present invention, the unipolar spin diode includes a first semiconductor region having a conductivity type and a spin polarization, and a second semiconductor region having a conductivity type that is same to the conductivity type of the first semiconductor and a spin polarization that is different from the spin polarization of the first semiconductor region. The first semiconductor region and the second semiconductor region are adjacent to each other so as to form a spin depletion layer therebetween, the spin depletion layer having a first side and an opposing second side. When a majority carrier in the first semiconductor region moves across the spin depletion layer from the first side of the spin depletion layer to the second side of the spin depletion layer, the majority carrier in the first semiconductor region becomes a minority carrier in the second semiconductor region. Moreover, when a majority carrier in the second semiconductor region moves across the spin depletion layer from the second side of the spin depletion layer moves to the first side of the spin depletion layer, the majority carrier in the second semiconductor region becomes a minority carrier in the first semiconductor region.
In one embodiment of the present invention, each of the first semiconductor region and the second semiconductor region comprises a p-type semiconductor layer, wherein the p-type semiconductor layer of the first semiconductor region is ferromagnetic, and the spin polarization of the first semiconductor region is either up or down. Moreover, the p-type semiconductor layer of the second semiconductor region is ferromagnetic, and the spin polarization of the second semiconductor region is either up if the spin polarization of the first semiconductor region is down, or down if the spin polarization of the first semiconductor region is up.
The majority carrier in the first semiconductor region can be a positive hole having a spin up, and the minority carrier in the first semiconductor region can be a positive hole having a spin down. Correspondingly, the majority carrier in the second semiconductor region is a positive hole having a spin down, and the minority carrier in the second semiconductor region is a positive hole having a spin up.
The majority carrier in the first semiconductor region can also be a positive hole having a spin down, and the minority carrier in the first semiconductor region is a positive hole having a spin up. Correspondingly, the majority carrier in the second semiconductor region is a positive hole having a spin up, and the minority carrier in the second semiconductor region is a positive hole having a spin down.
In other embodiment of the present invention, each of the first semiconductor region and the second semiconductor region comprises a n-type semiconductor layer, wherein the n-type semiconductor layer of the first semiconductor region is ferromagnetic, and the spin polarization of the first semiconductor region is either up or down. Moreover, the n-type semiconductor layer of the second semiconductor region is ferromagnetic, and the spin polarization of the second semiconductor region is either up if the spin polarization of the first semiconductor region is down, or down if the spin polarization of the first semiconductor region is up.
The majority carrier in the first semiconductor region can be an electron having a spin up, and the minority carrier in the first semiconductor region is an electron having a spin down. Correspondingly, the majority carrier in the second semiconductor region is an electron having a spin down, and the minority carrier in the second semiconductor region is an electron having a spin up.
The majority carrier in the first semiconductor region can also be an electron having a spin down, and the minority carrier in the first semiconductor region is an electron having a spin up. Correspondingly, the majority carrier in the second semiconductor region is an electron having a spin up, and the minority carrier in the second semiconductor region is an electron having a spin down.
The spin deletion layer may be characterized as one of a Neel wall and a Block wall, wherein the thickness of the spin deletion layer is at least partially determined by the ratio between the magnetic anisotropy energy and the magnetic stiffness of the first semiconductor region and the second semiconductor region.
Furthermore, the diode has a substrate of either an insulating material or a semi-insul
Flatté Michael Edward
Vignale Giovanni
Needle & Rosenberg P.C.
Nguyen Cuong Quang
The University of Iowa Research Foundation
LandOfFree
Unipolar spin diode and the applications of the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Unipolar spin diode and the applications of the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Unipolar spin diode and the applications of the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3004124