Rothschild v. Cree, Inc.

711 F. Supp. 2d 173, 2010 U.S. Dist. LEXIS 47223, 2010 WL 1909545
CourtDistrict Court, D. Massachusetts
DecidedMay 13, 2010
DocketCivil Action 10-10133-WGY
StatusPublished
Cited by8 cases

This text of 711 F. Supp. 2d 173 (Rothschild v. Cree, Inc.) is published on Counsel Stack Legal Research, covering District Court, D. Massachusetts primary law. Counsel Stack provides free access to over 12 million legal documents including statutes, case law, regulations, and constitutions.

Bluebook
Rothschild v. Cree, Inc., 711 F. Supp. 2d 173, 2010 U.S. Dist. LEXIS 47223, 2010 WL 1909545 (D. Mass. 2010).

Opinion

MEMORANDUM AND ORDER

YOUNG, District Judge.

I. INTRODUCTION

In the present case, the plaintiff Gertrude Neumark Rothschild charges the defendant Cree, Inc. with infringement of her U.S. Patents Nos. 4,904,618 (the “'618 Patent”) and 5,252,499 (the “'499 patent”). This memorandum and order addresses various motions brought by the parties, including a motion to dismiss for lack of standing, motions for claim construction, and motions for summary judgment.

II. BACKGROUND

A. Facts

1. The Patents-in-Suit

Rothschild owns two patents on methods of producing light emitting diodes (“LEDs”), which are at issue in this case:

The '618 Patent, entitled Process for Doping Crystals of Wide Band Gap Semiconductors, issued February 27, 1990, on an application filed August 22, 1988; and the '499 Patent, entitled Wide Band Gap Semiconductors Having Low Bipolar Resistivity and Method of Formation, issued October 12, 1993, on an application filed August 15,1988.

2. Introduction to the Technology

a. What are LEDS?

LEDs are used in a number of electronic devices ranging from display panels to billboards and even traffic lights. From a technological standpoint, LEDs are essentially p-n (positive-negative) junctions of wide band gap semiconductor materials. A semiconductor, as the name implies, is a material whose electrical conductivity is in the intermediate range between insulators and conductors. This means semiconductor material can conduct electricity under certain conditions, but not others. This characteristic makes the semiconductor a good medium for the control of electrical current.

b. Constructing Semiconductors

The semiconductors used to form the p-n junctions of LEDs are crystalline solids. The crystalline solid is a crystal lattice consisting of two types of atoms. Semiconductors can be made from either of two types of materials (1) a II-VI compound or (2) a III-V compound. To understand their differences, consider the periodic table of elements. The periodic table is arranged such that elements with similar properties fall into the same columns or groups. When an element from Group II of the periodic table, such as zinc (“Zn”) or cadmium (“Cd”), having two electrons in its outer shell, is combined with an element from Group VI, such as selenium (“Se”) or tellurium (“Te”), having six electrons in its outer shell, a compound having a normal eight electrons in its outer shell, such as zinc selenide (“ZnSe”), is formed. A crystal lattice consisting of a Group II element and a Group IV element is chemi *177 cally stable. This type of compound is called a II-VI compound. Likewise, a semiconductor may be formed by combining an element from Group III, such as gallium (“Ga”), having three electrons in its outer shell, with an element from Group V, such as arsenic (“As”), having five electrons in its outer shell. Again, this compound is also chemically stable. This type of compound is called a III-V compound,

c.n-type Semiconductors, p-type Semiconductors and the Concept of Doping

Doping is the process of intentionally introducing impurities into a semiconductor material (II-VI compound or III-V compound) to change its electrical properties. Likewise, a “dopant,” as defined in Rothschild v. Cree, Inc., No. 05-5939, 2007 WL 1314619 (S.D.N.Y. May 3, 2007) (“Rothschild I ") 1 “means an impurity added to a semiconductor material to alter its electronic properties.” Rothschild I at *3. If a dopant is incorporated into a semiconductor material, either during or after crystal growth, the electrical properties of the material may be changed in a useful manner. For example, if a II-VI compound such as ZnSe is doped with an element from Group V of the periodic table, such as nitrogen (“N”), having five electrons in its outer shell, the N atoms displace some of the Se atoms in the crystal lattice, thereby creating electron acceptors or “holes” in the crystal, making it a “p-type” material. Essentially, atoms with five electrons in their outer shell are introduced into the crystal and replace some of the existing atoms in the crystal lattice with six electrons in their outer shell. The result is that there is a deficit of electrons, and since compounds strive to have eight electrons in their outer shell, the compound wishes to accept electrons. Conversely, if the dopant is an element from Group III, such as Ga, having three electrons in its outer shell, its atoms displace some of the Zn atoms in the lattice, creating an excess of electrons in the crystal, making it an “n-type” material. Essentially, atoms with three electrons in their outer shell are introduced into the crystal and replace some of the existing atoms in the crystal lattice with two electrons in their outer shell. The result is that there is a surplus of electrons, and since compounds strive to have eight electrons in their outer shell, the compound desires to lose electrons.

d.Applying Voltage to the p-n Junction and the Emission of Light

A p-n junction consists of an n-type semiconductor at one end, a gap, and a p-type semiconductor at the other end. When a voltage is applied across the junction, electrons will move from the n-type material to fill the holes in the p-type material (flowing from negative to positive). As the electrons jump across the gap, the energy they lose in dropping from the conduction band (n-type material) to the valence band (p-type material) is released in the form of light. The wavelength or color of the light depends on the width of the gap between those bands in the particular material. For example, if the band gap is between 1.65 and 2.00 electron volts (“eV”), red light is produced; if it is below 1.65 eV, invisible infrared light or heat is produced. If the band gap is between 2.51 and 2.76 eV, blue light is produced; if it is above that range, violet or ultraviolet light is produced.

e.Difficulties in Doping, and the Concept of “Compensation”

Semiconductor materials with wide band gaps are more difficult to dope because *178 they more readily become “compensated.” To understand the concept of compensation, it is important to realize that, in practice, semiconductor materials contain internal impurities even before other impurities are introduced externally via doping. Compensation refers to the phenomenon in which impurities in the material itself supply the electrons to fill the holes in p-type material or supply the acceptors to receive the electrons in n-type material. In other words, if these internal impurities can satisfy the electro-chemical needs of the n-type or p-type semiconductor material, it is no longer necessary to incorporate the external dopants. Hence, the occurrence of compensation reduces the incorporation of the dopants into the crystal lattice and thereby increases the resistivity of the semiconductor. When there is high resistivity, electrons have difficulty jumping across the gap in the p-n junction, especially when it is very wide.

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711 F. Supp. 2d 173, 2010 U.S. Dist. LEXIS 47223, 2010 WL 1909545, Counsel Stack Legal Research, https://law.counselstack.com/opinion/rothschild-v-cree-inc-mad-2010.