Determination of Shallow Acceptor Concentration in SI ‐ GaAs from Steady‐State and Transient Microwave Photoconductivity Measurements

A non‐destructive characterization method using microwaves has been employed to determine the shallow acceptor concentration in undoped LEC semi‐insulating gallium arsenide  wafers. Both the above‐bandgap steady‐state and the below‐bandgap transient photoconductivities of  wafers are measured using a Ka‐band reflection‐type microwave setup in which there is no need to fabricate electrical contacts on  wafers. A photoconductivity model adopted from the two‐energy‐level defect model for undoped LEC semi‐insulating  is used to derive the relationship between the photoinduced microwave response and the concentration of shallow acceptors, mainly carbon. In the above‐ bandgap photoconductivity measurement, it is found that the steady‐state microwave response is inversely proportional to the square root of the shallow acceptor concentration. In the below‐bandgap photoconductivity measurement, the transient microwave response shows an initial fast decay and a second slower decay which has a Na‐related decay time constant. More than 30 undoped LEC  bulk wafers were used in our measurements to establish the correlation. These wafers have a carbon concentration ranging from  to , determined by LVM infrared absorption. Good agreements have been found between the shallow acceptor concentration obtained from the microwave photoconductivity measurements and the LVM carbon concentration.

Source:IOPscience

For more information, please visit our website:  www.semiconductorwafers.net,
send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com

Improved GaAs Bonding Process for Quasi‐Phase‐Matched Second Harmonic Generation

A multilayer stack of bonded GaAs wafers, each layer rotated 180° from the adjacent one, has been proposed for quasi‐phase‐matched second harmonic generation. Current bonding technology, however, often leads to unacceptable optical losses and, therefore, poor device performance. In this study, three sources of optical losses were investigated: (i) interfacial defects between the wafers, (ii) bulk defects within the wafers, and (iii) decomposition at the exposed outer surfaces. Surface losses due to incongruent evaporation were easily eliminated by repolishing the outer surfaces. However, to minimize the losses from interfacial and bulk defects, it was necessary to investigate the relationship between these defects and the processing parameters. It was found that an increase in temperature and/or time led to a decrease in interfacial defects, but an increase in bulk and surface defects. Optimized processing conditions were developed which permit the preparation of stacks containing over 50 layers of (100) GaAs wafers, and about 40 layers of (110) GaAs wafers. Optical losses as low as 0.1 to 0.3 % per interface (at 5.3 and 10.6 μm) were observed for the (110) oriented multilayer structures.

Source:IOPscience
For more information, please visit our website:  www.semiconductorwafers.net,
send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com

In Situ Surface Treatment of GaAs ( 100 ) Wafer in Metal Salt Electrolytes for Fabrication of Schottky Contact

The electrochemical behavior of n‐type  was investigated to find an optimum condition for in situsurface treatment in Ni salt electrolytes prior to the fabrication of  Schottky contacts by the wet method. Commercial machine‐polished  wafers with damaged crystal lattices did not show photoresponse and behaved exactly the same as a Ga metal electrode in the region of −0.1 to +0.5 V vs. . Photoresponse was observed after the removal of the damaged surface layer in . The in situsurface treatment of  was done by photoelectrochemical etching at +0.1 V in acidic nickel salt electrolyte followed by the fabrication of a  Schottky contact by applying negative potentials. Comparison of the fabrication methods is summarized in a table. The wet method is recommended for the fabrication of a  Schottky contact.

Source:IOPscience
For more information, please visit our website:  www.semiconductorwafers.net,
send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com

Wafer-scale processing technology for monolithically integrated GaSb thermophotovoltaic device array on semi-insulating GaAs substrate

This paper presents the entire fabrication and processing steps necessary for wafer scale monolithic integration of series interconnected GaSb devices grown on semi-insulating GaAs substrates. A device array has been fabricated on complete 50 mm (2 inch) diameter wafer using standard photolithography, wet chemical selective etching, dielectric deposition and single-sided metallization. For proof of concept of the wafer-scale feasibility of this process, six large-area series interconnected GaSb p–n junction thermophotovoltaic cells with each cell consisting of 24 small-area devices have been fabricated and characterized for its electrical connectivity. The fabrication process presented in this paper can be used for optoelectronic and electronic device technologies based on GaSb and related antimonide based compound semiconductors.

Source:IOPscience

For more information, please visit our website:  www.semiconductorwafers.net,
send us email at sales@powerwaywafer.com and powerwaymaterial@gmail.com