High-Performance InAs/GaAs Quantum Dots Infrared Photodetector With/Without Al 0.2 Ga 0.8 As Blocking Layers
- PDF / 123,735 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 54 Downloads / 189 Views
High-Performance InAs/GaAs Quantum Dots Infrared Photodetector With/Without Al0.2Ga0.8As Blocking Layers Zhengmao Ye, Joe C. Campbell Microelectronics Research Center, The University of Texas at Austin, 10,100 Burnet Rd., Bldg. 160, Austin, TX 78758, U.S.A. Zhonghui Chen, O. Baklenov, E. T. Kim, I. Mukhametzhanov, J. Tie, and A. Madhukar, Departments of Materials Science and Physics University of Southern California, Los Angeles, CA 90089-0241, U.S.A. ABSTRACT InAs/AlGaAs quantum dot infrared photodetectors based on bound-to-bound intraband transitions in undoped InAs quantum dots are reported. AlGaAs blocking layers were employed to achieve low dark current. The photoresponse peaked at 6.2 µm. At 77 K and –0.7 V bias the responsivity was 14 mA/W and the detectivtiy, D*, was 1010 cmHz1/2/W. INTRODUCTION Mid and far-infrared (3-20 µm) detection is a key technology for numerous commercial, military and space applications, e.g., night vision, thermal imaging, chemical analysis, nondestructive detecting, remote sensing, and missile guidance and defense. Due to the long carrier capture and relaxation times, quantum dot infrared photodetectors (QDIPs) have the potential for lower dark current and higher photoresponse than quantum well infrared photodetectors (QWIPs). Most importantly, the three-dimensional confinement of electrons in the quantum dots permits QDIPs to operate in the normal incidence mode, unlike QWIPs which are not sensitive to radiation that is incident perpendicular to the quantum wells [1]. To date, there have been several papers on InAs/GaAs, InGaAs/GaAs and InGaAs/InGaP QDIPs [2]-[10]. Most of the devices employed a doped active region, which resulted in high dark current. In this paper, we report an InAs/GaAs QDIP with unintentionally doped active region and AlGaAs barrier layers (sample A). The AlGaAs layers act as a blocking layer [6]-[10] for dark current, as first demonstrated in Ref. 6. The devices reported here have demonstrated low dark current, low noise, and high detectivity. DEVICE STRUCTURES AND FABRICATIONS The InAs QDIPs studied in this work belong to the class of n-i-n structure QDIPs (Figure 1) under examination by us [6][7]. The samples were grown on semi-insulating GaAs (001) substrates by solid-source molecular beam epitaxy. Five layers of 3 monolayer (ML) InAs quantum dots were inserted between highly Si-doped top and bottom GaAs contact layers. The punctuated island growth technique was used to grow the quantum dots [11]. The GaAs spacer layers between the contact layers and the nearest quantum dot layer had a thickness of 219 ~ 239 ML. 30 ML GaAs regions were used as the quantum dot cap layers. In order to reduce the dark current, four pairs of AlAs/GaAs (1 ML/ 4 ML) were introduced below the quantum dot layers and on the top of the GaAs cap layers (sample A). A similar QDIP without blocking layers H9.17.1
IR Light
Bias InAs QDs
n+ GaAs contact GaAs
AlGaAs
GaAs
n+ GaAs contact SI GaAs substrate
Fig. 1 Schematic of InAs/GaAs QDIP structure (e.g. with AlGaAs blocking layers
Data Loading...
