Chapter 1 Electronic and Photonic Materials - DMS. Diluted Magnetic Semiconductor (DMS)

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Tyrone Pope
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1 Diluted Magnetic Semiconductor (DMS) 1

2 Properties of electron Useful! Charge Electron Spin? Mass 2

3 Schematic of a Spinning & Revolving Particle Spinning Revolution 3

4 Introduction Electronics Industry Uses charge of electron Integrated circuits and high-frequency devices made of semiconductors, used for information processing and communications Storage Industry Uses spin of materials, magnetism Mass storage of information indispensable for information technology is carried out by magnetic recording (hard disks, magnetic tapes, magneto optical disks) Definition - DMS Semiconductor Charge Magnetic Spin Dilute or diluted magnetic semiconductors (DMS) also referred to as semi magnetic semiconductors, are alloys whose lattices are made up in part of substitutional magnetic atoms Semiconductors with dilute concentration of magnetic dopants 4

5 Important! The most important feature of these materials is carrier mediated magnetism which can be easily controlled with voltage The advantage is that, unlike the conventional magnets, DMS are compatible with semiconductors and can be used as efficient sources for spin injection. 5

6 An Experiment! 6

7 Will the magnet move (magnetic) ice cube??? 7

8 (Magnetic) Ice cube = (Magnetic) Semiconductor!!! 8

9 Importance of magnetic ions 9

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11 Materials for DMS II VI II-VI Transition Metal Zn S ZnS Mn or Fe or Co Cd Te CdTe Mn or Fe or Co Cd Se CdSe Mn or Fe or Co IV VI IV-VI Transition Metal Pb Se PbSe Mn or Fe or Co Sn Te SnTe Mn or Fe or Co V VI V-VI Transition Metal Ga As GaAs Mn or Fe or Co In Sb InSb Mn or Fe or Co 11

12 Formation of DMS 12

13 Aspects of DMS Coexistence and interaction of two different electronic sub systems: delocalized conduction (s-type) and valence (p-type) band electrons and localized (d or f-type) electrons of magnetic ions. The spd exchange interaction leads to strong band splitting, which result in giant magneto optical effects The solubility limit of magnetic elements in III-V semiconductors is very low, but in order to have ferromagnetism in DMS, a sizable amount of magnetic ions are needed. The highest conclusively reported Tc of DMS is around 110 K for 5 % doped GaAs. 13

14 Applications of DMS Charge and spin degrees of freedom accommodated into a single material exhibits interesting magnetic, magneto-optical, magnetoelectronic and other properties An inherent advantage of magnetoelectronics over electronics is the fact that magnet tend to stay magnetized for long. DMS materials are very attractive for integration of photonic (lightemitting diodes), electronic (field effect transistors), and magnetic (memory) devices on a single substrate 14

15 Some important application areas of DMS Photonics plus spintronics (Spin+electronics = Spintronics) Improved spin transistor Transistors spin toward quantum computing Magnetic spins to store quantum information Microscope to view magnetism at atomic level Ballistic magneto resistance Missile guidance Fast accurate position and motion sensing of mechanical components in precision engineering and in robotics In automotive sensors 15

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EXTRINSIC SEMICONDUCTOR

EXTRINSIC SEMICONDUCTOR In an extrinsic semiconducting material, the charge carriers originate from impurity atoms added to the original material is called impurity [or] extrinsic semiconductor. This Semiconductor