Terahertz Ionization of Highly Charged Quantum Posts in a Perforated Electron Gas

详细信息    查看全文

• 作者：Christopher M. Morris ; Dominik Stehr ; Hyochul Kim ; Tuan-Anh Truong ; Craig Pryor ; Pierre M. Petroff ; Mark S. Sherwin
• 刊名：Nano Letters
• 出版年：2012
• 出版时间：March 14, 2012
• 年：2012
• 卷：12
• 期：3
• 页码：1115-1120
• 全文大小：867K
• 年卷期：v.12,no.3(March 14, 2012)
• ISSN：1530-6992

文摘

鈥淨uantum posts鈥?are roughly cylindrical semiconductor nanostructures that are embedded in an energetically shallower 鈥渕atrix鈥?quantum well of comparable thickness. We report measurements of voltage-controlled charging and terahertz absorption of 30 nm thick InGaAs quantum wells and posts. Under flat-band (zero-electric field) conditions, the quantum posts each contain approximately six electrons, and an additional 2.4 脳 10¹¹ cm^鈭? electrons populate the quantum well matrix. In this regime, absorption spectra show peaks at 3.5 and 4.8 THz (14 and 19 meV) whose relative amplitude depends strongly on temperature. These peaks are assigned to intersubband transitions of electrons in the quantum well matrix. A third, broader feature has a temperature-independent amplitude and is assigned to an absorption involving quantum posts. Eight-band k路p calculations incorporating the effects of strain and Coulomb repulsion predict that the electrons in the posts strongly repel the electrons in the quantum well matrix, 鈥減erforating鈥?the electron gas. The strongest calculated transition, which has a frequency close to the center of the quantum post related absorption at 5 THz (20 meV), is an ionizing transition from a filled state to a quasi-bound state that can easily scatter to empty states in the quantum well matrix.

Keywords:

Terahertz; quantum dots; quantum posts; electron gas; ionization