Search for free holes in InN:Mg-interplay between surface layer and Mg-acceptor doped interior

Abstract

We measured lateral ac transport (up to 20 MHz), thermopower, as well as resistivity and Hall effect in InN:Mg samples with various Mg content. The sign of the Hall effect for all the samples was negative (electrons), however, the thermopower (α) measurements have shown the p-type sign of α for moderate Mg content—in the window centered around 1×1019 cm−3. Further overdoping with Mg yields donor type of defects and the change of thermoelectric power sign. The ac measurements performed as a function of frequency revealed that in both samples exhibiting and nonexhibiting p-type sign of thermopower, the n-type inversion layer at the surface does not prevent the electric contact to the bulk layer. Therefore we conclude that the n-type Hall effect invariably reported for all the Mg-doped samples originates from electron domination in mobility-weighted contributions of both types of carriers.

Revealing of the transition from n- to p-type conduction of InN:Mg by photoconductivity effect measurement

“…That is the reason why all the reported Mg-doped InN samples showed apparently n-type conduction91112. On the contrary, thermopower measurements have been confirmed to show buried p-type conduction111215161718. The key difference of thermopower measurement over Hall-effect measurement is that the total Seebeck coefficient S is weighted by n i μ i 13141719 ( S total = ( n n μ n S n + n p μ p S p )/( n n μ n + n p μ p )) instead of in the Hall coefficient and thus the relative contribution from the accumulated electrons would be greatly pushed down, where the Seebeck coefficient S is positive (S > 0) for holes and negative (S < 0) for electrons.…”

Effect of charged dislocation scattering on electrical and electrothermal transport inn-type InN

“…a charged dislocation density of 10 9 cm −2 corresponds to an electron density of 2 × 10 16 cm −3 . Finally, the charge accumulation that would be expected to occur around charged line defects has important implications as well; it is possible that vertical conduction along threading dislocations is one reason that pn junctions in InN have been hard to produce, in spite of recent reports confirming p-type conduction in Mg-doped InN films 14,[52][53][54] . from several images appears to be as low as 1×10 9 cm −2 although the roughness of the films and the pits which form in the foil as a result add some uncertainty to this determination.…”

Advantage of In- over N-polarity for disclosure of p-type conduction in InN:Mg

“…Such observation is still very unique and takes place only in the so called "p-type window" centered at about 1 Â 10 19 cm À3 of [Mg]. 2,4,5 The aim of this paper was to find out whether a particular (In or N) growth polarity of InN may be beneficial or detrimental to the appearance of p-type conduction in this multicarrier system. Such a possibility was suggested in Ref.…”