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