Micromachined III-V cantilevers for AFM-tracking scanning Hall probe microscopy

In this paper we report the development of a new III-V cantilever-based atomic force sensor with piezoresistive detection and an integrated Hall probe for scanning Hall probe microscopy. We give detailed descriptions of the fabrication process and characterization of the new integrated sensor, which will allow the investigation of magnetic samples with no sample preparation at both room and cryogenic temperatures. We also introduce a novel piezoresistive material based on the ternary alloy n+-Al0.4Ga0.6As which allows us to achieve a cantilever deflection sensitivity ΔR/(RΔz) = 2 × 10-6 Å-1 at room temperature

Modeling and process control of MOCVD growth of InAlGaAs MQW structures on InP

We have developed a model which integrates calculation of InAlGaAs multiple quantum well (MQW) transition energies using the envelope function approximation with a statistical analysis of the PL emission wavelength, net strain and MQW period measured for a variety of MQW designs grown by MOCVD. The model relates the measured MQW parameters directly to MOCVD process parameters, allowing an accurate prediction of the process parameters required to grow a specified MQW design. This greatly reduces the need to grow and characterize individual calibration layers. The difference of the measured and predicted MQW parameters is recorded run-to-run over time, which allows process variability to be analyzed across a number of process parameters with intentional variations to grow different MQW designs. Crown Copyright \ua9 2013.Peer reviewed: YesNRC publication: Ye

MOCVD based zinc diffusion process for planar InP/InGaAs avalanche photodiode fabrication

We investigated the diffusion of zinc into InP/InGaAs avalanche photodiode structures using dimethylzinc in an MOCVD reactor. Diffusion profiles were measured by secondary ion mass spectrometry and compared with cleaved cross-sections imaged by scanning electron microscopy, in order to accurately target the diffusion depth for device fabrication. The dependence of the diffusion depth on the diffusion temperature, partial pressures of dimethylzinc and phosphine, and diffusion time is reported. Diffused devices exhibit, in some cases, a step increase in dark current at or near the punch-through voltage. We show that the dark current above the punch-through voltage is proportional to the junction area and originates in the bulk of the material. The dependence of this bulk dark current contribution on the diffusion process parameters has been studied in detail, and a reduction of three orders of magnitude was achieved.Peer reviewed: YesNRC publication: Ye

Optimization of MOCVD-diffused p-InP for planar avalanche photodiodes

We investigate the materials properties and dark currents of planar InP/InGaAs avalanche photodiodes (APDs) in which the p-dopant, Zn, is introduced by diffusion in an MOCVD reactor using dimethylzinc (DMZn) as the source. APD dark currents are compared with low-temperature photoluminescence (PL), electrochemical capacitance-voltage (ECV) and secondary ion mass spectroscopy (SIMS) measurements of layers diffused under the same set of conditions. Device dark currents exhibit both surface-related and bulk contributions, with the bulk contribution appearing as a step increase in the current near the punch-through voltage. The bulk dark current contribution depends on the diffusion process parameters and is correlated with the total Zn incorporation and the intensities of the InP and InGaAs PL peaks. A variation of three orders of magnitude is observed in the bulk dark current contribution as diffusion conditions are varied. \ua9 2013.Peer reviewed: YesNRC publication: Ye

Narrow channel breakdown in GaAs/AlGaAs Heterostructures

We have studied the breakdown characteristics of a narrow two-dimensional electron gas channel in GaAs/AlGaAs heterostructures over a wide temperature range before and after illumination. We report on the behaviour of the breakdown current, the asymmetry of the Shubnikov-de Haas oscilations and the appearance of step-like structures in the diagonal resistivity \u3c0vv. The step-like features are not consistent with a quasi-elastic inter Landau level scattering mechanism. \ua9 1987.Peer reviewed: YesNRC publication: Ye

Integrated piezoresistive sensors for atomic force-guided scanning Hall probe microscopy

We report the development of an advanced sensor for atomic force-guided scanning Hall probe microscopy whereby both a high mobility heterostructure Hall effect magnetic sensor and an n-Al0.4Ga0.6As piezoresistive displacement sensor have been integrated in a single III–V semiconductor cantilever. This allows simple operation in high-vacuum/variable-temperature environments and enables very high magnetic and topographic resolution to be achieved simultaneously. Scans of magnetic induction and topography of a number of samples are presented to illustrate the sensor performance at 300 and 77 K

InAs/InP quantum dot laser devices around 1550 nm for fiber communications

We report on our most recent results on quantum dot (QD) laser devices around 1550 nm based on InAs/InP QD gain materials. These devices include monolithic QD multi-wavelength lasers (MWLs), mode-locked lasers (MLLs) and distributed feedback (DFB) lasers. The performance and potential applications of fiber communications will be discussed. \ua9 2011 IEEE.Peer reviewed: YesNRC publication: Ye