Spintronics( 自旋電子學 )-GaN-based 稀磁性半導體 (diluted magnetic semiconductors,DMSs)
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Transcript of Spintronics( 自旋電子學 )-GaN-based 稀磁性半導體 (diluted magnetic semiconductors,DMSs)
Spintronics( 自旋電子學 )-GaN-based稀磁性半導體 (diluted magnetic
semiconductors,DMSs)
學生:黃鋒文
Outline
• paper research• Abstract
• Introduction
• Experiment
• Result and discussion
• Conclusion
Electric field control of room temperature ferromagnetism in Ⅲ-N dilute magnetic
semiconductor films
APL 94, 132505
Abstract
• 1.GaMnN/p-GaN SLS/n-GaN(i-p-n)• 2.electrical field control • 3.room temperature• 4.on n-GaN paramagnetic• 5.on p-GaN ferromagnetism• 6.holes mediated (carrier induced)• 7.anomalous Hall effect
Introduction
• 過去已發展出電控鐵磁性的材料 (GaMnAs)但是居禮溫度過低﹗ ( 大約110K)
• GaMnN: 2000年理論預測室溫鐵磁性 + 2001實驗首度證實 ( 以MOCVD+固態擴散 )
• 2004年首度直接以 MOCVD成長出 GaMnN + 研究鐵磁性機制來源[carrier transfer at (GaMnN)/GaN : Mg interface]
• 2005年提出磁性來源理論機制: exchange interaction between Mn ions and holes in GaMnN DMS FM control number of interacting holes
Experiment• 1. 以 MOCVD 成長 GaMnN/p-(Al0.2Ga0.8N/GaN)/n-GaN/GaN/sapphire (c-plane) (i-p-n) /
Mn sources: (EtCp)2Mn
• 2.GaMnN : 0.5μm Mn dopant concentration 1020 cm-3 (SIMS)
• 3.p-type region : Mg-doped (Al0.2Ga0.8N/GaN) SLSs – period :16.6 nm :統稱為: p-GaN
• 4. 磁性量測: AGM
• 5. 元件 size 2*2 mm2 / contact on p-GaN and n-GaN
• 6. 若 GaMnN 成長在 sapphire 上 ( 沒有 p-GaN-SLS) 順磁性 • 若 GaMnN 成長在 p-GaN template 鐵磁性 • ( 並與 annealing condition 有關 - 因熱處理可活化 Mg-doped GaN 的 acceptor dopant
and enhances the hole concentration at RT )
• 7. 實驗:• a. 固定 GaMnN 厚度 - 零偏壓下 - 變化 p-GaN 厚度( + annealing condition )• b. 固定 GaMnN 厚度 - 固定 p-GaN 厚度 - 變化偏壓• c. 正常與異常霍爾效應
High sheet resistance of the low mobility p-GaN layer
The very high forward bias series resistance of this rectifying GaN p-n junction
Result and discussion
Result and discussion
n+pi
Wp
Xp
Interaction length
Mn spin itinerant holes
interaction strength MsPS : Only the holes near the GaMnN/p-GaN interface interact with localized Mn ion spins
The higher the hole concentration, the stronger the ferromagnetism
penetration depth for the hole wave function
<30nm
Thermal annealing of Mg-doped GaN activates the acceptor dopant and enhances the hole concentration at RT
66nm PM due to insufficient mediating holes
Hole depletion fully
Wp=161nm at zero bias
Result and discussion
n+pi
Wp
Xp
Interaction length
Mn spin itinerant holes
interaction strength MsPS : Only the holes near the GaMnN/p-GaN interface interact with localized Mn ion spins
The higher the hole concentration, the stronger the ferromagnetism
penetration depth for the hole wave function
FM
PM
<30nm
Wp~0.221μm
Wp~0.25μm
Xp=0.25μm
Wp=161nm at zero bias
Result and discussion semiconductor
LinearOrdinary Hall effect
RHall(B)=(R0/d)B
Hall concentration ~ 1018 cm-3
FM semiconductornonlinear
Anomalous Hall effect
RHall(B)=(R0/d)B +(Rs/d)M
ΔRHall=RHall(B)-RHall(0)
The magnetic field splits the GaN valanceband, which leads to an exchange interaction betweenholes and localized Mn 3d spins, resulting in the AHE
For reversed bias holes in the p-GaN
are depleted total number of holes that interact with Mn 3d spins decreases OHE dominates
與 AGM 結果 一致
Thanks for your attention