Spintronics( 自旋電子學 )-GaN-based 稀磁性半導體 (diluted magnetic semiconductors,DMSs)

1. Spintronics(自旋電子學)-GaN-based稀磁性半導體(diluted magnetic semiconductors,DMSs) 學生：黃鋒文

2. Outline • paper research • Abstract • Introduction • Experiment • Result and discussion • Conclusion

3. Electric field control of room temperature ferromagnetism in Ⅲ-N dilute magnetic semiconductor films APL 94, 132505

4. 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

5. 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

6. 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annealingcondition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（ + annealingcondition ） • 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

7. Result and discussion Highsheet resistance of the low mobility p-GaN layer The very high forward bias series resistance of this rectifying GaN p-n junction

8. Result and discussion Thermal annealing of Mg-doped GaN activates the acceptor dopant and enhances the hole concentration at RT penetration depth for the hole wave function Wp=161nm at zero bias ＜30nm Interaction length p i n+ Wp Hole depletion fully Xp 66nm PM due to insufficient mediating holes Mn spin itinerant holes Ms interaction strength The higher the hole concentration, the stronger the ferromagnetism PS : Only the holes near the GaMnN/p-GaN interface interact with localized Mn ion spins

9. Result and discussion Xp=0.25μm penetration depth for the hole wave function ＜30nm FM Interaction length p i n+ Wp~0.221μm PM Wp Wp~0.25μm Xp Wp=161nm at zero bias Mn spin itinerant holes Ms interaction strength The higher the hole concentration, the stronger the ferromagnetism PS : Only the holes near the GaMnN/p-GaN interface interact with localized Mn ion spins

10. Result and discussion semiconductor Linear Ordinary Hall effect FM semiconductor nonlinear Anomalous Hall effect RHall(B)=(R0/d)B RHall(B)=(R0/d)B +(Rs/d)M Hall concentration ～1018 cm-3 The magnetic field splits the GaN valance band, which leads to an exchange interaction between holes 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 ΔRHall=RHall(B)-RHall(0)

11. Thanks for your attention