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-(Al 0.2 Ga 0.8 N/GaN)/n-GaN/GaN/sapphire (c-plane) (i-p-n) / Mn sources: (EtCp) 2 Mn 2.GaMnN ： 0.5μm Mn dopant concentration 10 20 cm -3 (SIMS) 3.p-type region ： Mg-doped (Al 0.2 Ga 0.8 N/GaN) SLSs – period :16.6 nm ：統稱 為： p-GaN 4. 磁性量測： AGM 5. 元件 size 2*2 mm 2 / 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

7. 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

8. n+n+ p i Wp Xp Interaction length Mn spin itinerant holes interaction strength Ms PS : 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 W p =161nm at zero bias

9. Result and discussion n+n+ p i Wp Xp Interaction length Mn spin itinerant holes interaction strength Ms PS : 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 W p ~0.221μm Wp~0.25μm Xp=0.25μm W p =161nm at zero bias

10. Result and discussion semiconductor Linear Ordinary Hall effect R Hall (B)=(R 0 /d)B Hall concentration ～ 10 18 cm -3 FM semiconductor nonlinear Anomalous Hall effect R Hall (B)=(R 0 /d)B +(R s /d)M ΔR Hall =R Hall (B)-R Hall (0) 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

11. Thanks for your attention