Effect of a current blocking barrier on a 2–6 μm p-GaAs/AlGaAs heterojunction infrared detector

Abstract

We report the performance of a 30 period p-GaAs/Al x Ga 1Àx As heterojunction photovoltaic infrared detector, with graded barriers, operating in the 2-6 lm wavelength range. Implementation of a current blocking barrier increases the specific detectivity (D*) under dark conditions by two orders of magnitude to $1.9 Â 10 11 Jones at 2.7 lm, at 77 K. Furthermore, at zero bias, the resistance-area product (R 0 A) attains a value of $7.2 Â 10 8 X cm 2 , a five orders enhancement due to the current blocking barrier, with the responsivity reduced by only a factor of $1.5. Published by AIP Publishing.[http://dx.doi.org/10.1063/1.4952431] Infrared (IR) detectors and imaging systems are becoming increasingly important in a diverse range of military and civilian applications. In recent years, significant attention has been paid to incorporating current blocking architectures into detector designs. For example, AlGaAs current blocking layers have been utilized in quantum dot IR photodetectors (QDIPs) both to enhance performance [1][2][3][4][5][6] and to achieve elevated operating temperatures. [7][8][9] Similarly, in type II InAs/ GaSb superlattice (T2SL) IR photodetectors, majority carrier (hole) blocking layers have been implemented, 10 as well as electron blocking and hole blocking unipolar barriers in complementary barrier infrared detectors (CBIRD) 11 and p-type-intrinsic-n-type (PbIbN) photodiodes. 12 Furthermore, dark current suppressing structures were also demonstrated, such as conduction band barriers in nBn photodetectors 13,14 and XBn barrier photodetectors. 15 In general, the main goal in these architectures is to lower the dark current, but with a relatively small compromise to the photocurrent, thus achieving a significant improvement in the specific detectivity (D*).Due to the mature growth and established processing technology of p-GaAs/Al x Ga 1Àx As, these materials systems have become increasingly attractive for demonstrating heterojunction interfacial workfunction IR photodetectors (HEIWIP), 16 which operate up to room temperature. 17 Furthermore, replacing the constant Al x Ga 1Àx As barrier with a graded barrier, achieved by tuning the Al mole fraction (x), was found to enable photovoltaic operation as well. 18 This is advantageous over photoconductive operation as it offers thermal noise limited performance and reduced power consumption. In this letter, we report the effect of a current blocking barrier (CBB) on a 30 period p-GaAs/Al x Ga 1Àx As IR detector with graded barriers, which shows a photoresponse at 77 K in the $2-6 lm range under photovoltaic operation. We observe an approximately five orders of magnitude higher resistance-area product (R 0 A) at zero bias, resulting in a two orders of magnitude improvement in D*, with the responsivity compromised only by a factor of $1.5 at zero bias, compared to performance without the CBB.A p-GaAs/Al x Ga 1Àx As heterojunction IR detector was grown on a semi-insulating GaAs substrate by molecular beam epitaxy 19 ( Fig. 1(a)). The active region of the ph...

Study of infrared photodetectors with wavelength extension mechanism

“…We note that the experimentally measured dark current deviates only for small values of the applied biases, and mostly for positive bias conditions. One of the possible reasons for this behavior may be attributed to the non-uniform distribution of the applied bias due to presence of multiple resistive elements [4,11] , that is, energy barriers with different barrier heights. At low biases, mostly the dc voltage is dropped across the graded barrier due to higher barrier energy, making the effective electric field across it much higher than the value under uniform distribution.…”

“…Furthermore, free-carrier absorption increases with the wavelength [3] as . Using the p-GaAs/Al x Ga 1-x As heterostructures for the internal photo-emission, can be tuned by changing the Al mole fraction x in the Al x Ga 1-x As barrier region to design the detectors covering mid-IR to far-IR ranges [4,5]. Unlike these conventional approaches, an alternative mechanism was discovered that demonstrated an extended wavelength photoresponse in the spectral range to very-long-wavelength IR (VLWIR) range, far beyond the limit of in corresponding to mid-IR range [6][7][8].…”

Recent Progress on Extended Wavelength and Split-Off Band Heterostructure Infrared Detectors

“…Many scientists have thus used refractive indexes, bandgap, effective masses and mobilities of charge carriers, and the electron energy spectrum advantages of semiconductor heterostructures with various material combinations, architectures, and doping densities for the futuristic scientific, technical and biomedical applications [4][5][6][7][8][9][10]. The examples include GaAs/AlGaAs heterostructures [11], which have been well-studied for its potential application in high-speed digital and optoelectronic devices [12] including diode lasers [13], light-emitting diodes [14], solar cells [15] and optical detectors [8,[16][17][18][19][20]. The material advantage of GaAs/AlGaAs provides excellent uniformity and large arrays.…”

Studies on plasma assisted molecular beam epitaxial growth of GaN-based multilayer heterostructures on Si for photodetector application

“…However, limited by the simple structure used, it is difficult to obtain both IR-and UV-response for dual band detection. Modified on the structure described in Fig Many dual band detectors have been developed for near-, mid-and far-infrared regions using homo-or hetero-junction structures based on the group III-As material systems [180][181][182][183][184][185][186][187]. Similar structures can be employed using GaN/AlGaN multiple layers for UV and IR detection, but the output signal will be a mixed one, necessitating the use of filters to separate the UV and IR components.…”

“…6.19 shows the dark current characteristics when positive bias was applied to the top electrode and bottom electrode was grounded. The asymmetric dark current is caused by the asymmetric barrier designed in this detector structure [187,267]. Samples 1 to 10 were grown with different Al-composition on different substrates and Table 6.3 AlGaN/GaN multilayer structure grown on different substrates with different designs for UV detector Table 6.4 AlGaN/GaN multilayer structure grown on different substrates with different designs for UV detector the devices were fabricated with different device designs, dark current density ranging between 10 1 to 10 3 A/m 2 was achieved for devices with similar mesa area.…”