Laboratory fellows are the enemy of theory. Although so many times they work vainly, they indeed believe that everything is possible, if you do. For example, last year, we got the first fingerprint of p-type InN (1), which is in the same boat with GaN, AlN and ZnO hated by doping theory because of their valence band edges locating far below the Fermi level stabilization energy EFS, located 4.9 eV below the vacuum level (2).

Besides the valence band edge, the hinders in InN for p-type doping, such as low position of the conduction band edge and donorlike surface defects that prefer to pin the surface Fermi energy at EFS, also make a p-doping hard to be accessed (2, 3).

So when R. E. Jones et al. finally fulfilled this primary penetration in InN, by isolating the effects of the n-type conductivity in the surface accumulation layer with a rectifying contact to InN using an electrolyte (1), they justly feel happy, because "alloys of the two compounds (GaN & InN) could be combined to make a full-spectrum solar cell", reports Paul Preuss in this issue (5). 

However, the garden is full of stones. One such, for example, is just how to make a solid contact with other one, thinks Liang Cao (6). This longstanding problem surely links to the origin of the p-doing difficulty. If we can not bypass the barrier using liquid contact like that of PRL's report (1), what can we do? □  

* Lin Pu is in the Physics Department of Nanjing University, Nanjing 210093, CHINA.